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THE  GIFT  OF  MR.  ALFRED  GWYNNE  VANDERBILT 


UBRARY 

RAILROAD  BRANCH 

YOUNG    MEN'S   CHRISTIAN    ASSOCIATION 

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NATIONAL  ASSQCMriON 


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OF 


CEMENT    UiitFt§:Tr.:: 


PROCEEDINGS 


OF  THE 


Eighth  Annual  Convention 

Held  at  Kansas  City,  Mo., 
March  11,  12,  13,  14,  15,  16,  1912 


Volume  VIII 


EDITED  UNDER  DIRECTION  OF  THE  PRESIDENT 

BY  THE  SECRETARY 


PUBLISHED    BY   THE  ASSOCIATION 
1912 


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•    •  •••     •     •••••••      • 

••    :•:  ••  •!••      •  •  •  • :  •••: 


•  ••;•      •      •••    ••    • 

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Comaxan  1915  bt  thb  Ambbioak  Concbbtb  Imwitutb 


The  ABBOoiBtioii  is  not  reaponaible,  as  a  body,  for  the  statements  and  opinions 
advanced  in  iU  publications. 


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CONTENTS. 


PAOfc 

Personnel  of  Officers 6 

Personnel  of  Sectional  Committees 7 

Personnel  of  Past  Officers 9 

Charter 10 

By-Laws 11 

Summary  of  Proceedings,  Eighth  Annual  Convention 16 

Annual  Address  by  the  President,  European  Practice  in  Concrete  Con- 
struction— Richard  L.  Humphrey 31 

Report  of  the  Committee  on  Reinforced  Concrete  and  Building  Laws — 

A.  E.  Lindau,  Chairman 61 

Disciission 158 

The  Testing  of  Reinforced  Concrete  Buildings  Under  Load — W.  A. 

Slater 168 

The  Design  of  Concrete  Flat  Slabs— F.  J.  Trelease 218 

Discussion 251 

The  Practical  Design  of  Reinforced  Concrete  Flat  Slabs — Sanford  E. 

Thompson 254 

Discussion 274 

The  Design  of  Concrete  Grain  Elevators — E.  Lee  Heidenreich 277 

Discussion 288 

Report  of  the  Committee  on  Measuring  Concrete — ^Robert  A.  Cummings, 

Chairman 290 

Proposed  Standard  Methods  for  the  Measurement  of  Concrete  Work 301 

Concrete  Retaining  Walls — John  M.  Meade 308 

Discussion 311 

Reinforced  Concrete  Piles — Robert  A.  Cummin^ 312 

The  Handling  of  Concrete  in  the  Construction  of  the  Panama  Canal — S.  B. 

Williamson 326 

Use  of  Concrete  in  the  Fourth  Avenue  Subway,  Brooklyn,  N.  Y. — Fred- 
erick C.  Noble 361 

The  Use  of  Reinforced  Concrete  in  Hypochlorite  Water  Purification 

Works— Walter  M.  Cross 372 

Design  and  Construction  of  the  Estacada  Dam — H.  V.  Schreiber 376 

Unit  Cost  of  Reinforced  Concrete  for  Industrial  Buildings — C.  S.  Allen . .  400 
Reinforced  Concrete  Convention  Hall  at  Breslau,  Germany — S.  J.  Trauer.  406 
The  Suitability  of  Concrete  for  Gas  Holder  Tanks— Herbert  W.  Ab-ich . .  412 
Protection  of  Steel  in  Catskill  Aqueduct  Pipe  Siphons — Alfred  D.  Flinn. .  424 

A  Fireproof  School  of  Concrete — Theodore  H.  Skinner 444 

Tlie  Plresent  Status  of  Unit  Concrete  Construction — ^James  L.  Darnell. .  .  455 
Discussion 469 

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Contents. 


PADS 

Report  of  Committee  on  Specifications  and  Methods  of  Tests  for  Concrete 

Materials — Sanford  E.  Thompson,  Chairman 473 

Aggregates  for  Concrete — William  M.  Kinney 486 

Discussion 497 

Field  Inspection  and  Testing  of  Concrete — G.  H.  Bayles 501 

Comparative  Tests  of  the  Strength  of  Concrete  in  the  Laboratory  and  in 

the  Field— Rudolph  J.  Wig 522 

Discussion 526 

The  Necessity  for  Field  Tests  of  Concrete — Fritz  X'on  Emperger 530 

Discussion 537 

Report  of  the  C'ommittee  on  Treatment  of  Ccmcrete  Surfaces — L.  C. 

Wason,  Chairman 539 

Discussion 547 

Cement   Coatings — F.  J.  Morse 552 

Discussion 561 

Review  of  the  Present  Status  of  Iron  Portland  Cement — P.  H.  Hates. . .  .  566 

Marine  or  Iron  Ore  (Vments — Herman  E.  lirovvn 578 

Iron  Ore  Cement — Arthur  E.  Williams 597 

Discussion  on  Iron  Ore  Cement 613 

Flat  Slab  Concrete  Bridges— William  H.  Finley 616 

Concrete  Highway  Bridges — Walter  Scott  Gearhart 621 

Concrete  Bridges — Daniel  B.  Luten 631 

Discussion  on  Concrete  Bridges 641 

Report  of  Committee  on  Roadways,  Sidewalks  and  Floors — C.  W.  Boyn- 

ton,  Chairman 644 

Standard  Specifications  for  Portland  Cement  Sidewalks 645 

Standard  Specifications  for  Concrete  Roads  and  Street  Pavements 651 

Standard  Specifications  for  Concrete  Curb  and  C^oncret(>  Curb  and  (Gutter  658 

Standard  Specifications  for  Plain  Concrete  Floors 665 

Standard  Specifications  for  Reinforced  Concrete  Floors 671 

Discussion  on  Concrete  Floors 676 

An  Improved  Concrete  Pavement — E.  W.  Groves 683 

Cement  Paving  as  Constructed  at  Mason  City,  Iowa — F.  P.  Wilson.  .  .   689 

Discussion  on  Concrete  Roads 694 

Report  of  the  Committee  on  Building  Blocks  and  Cement  Products — 

P.  H.  Hudson,  Chairman 699 

Recommended  Practice  for  Plain  Concrete  Drain  Tile 700 

Recommended    Practice    for    Concrete    Architectural    Stone,    Building 

Block  and  Brick 703 

Standard  Specifications  for  Concrete  Architectural  Stone,  Building  Block 

and  Brick 707 

Standard  Building  Regulations  for  the  Use  of  Concrete  Architectural 

Stone,  Building  Block  and  Brick 710 

Method  of- Testing  Cement  Pipe — Arthur  N.  Talbot  and  Duflf  A.  Abrams  713 
Advantages  and  Durability  of  Cement  Sewer  Pipe — Gustave  Kaufman. .  720 
The  Manufacture  and  Use  of  Cement  Drain  Tile — C^harles  E.  Sims 727 

Discussion 732 


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Contents. 


PAGE 

Modern    Methods   of    Manufacturing    Concrete   Products — Robert   F. 

Havlik 740 

Notes  on  Reinforced  Concrete  Telegraph  Poles — George  Gibbs 757 

Concrete  Fence  Posts — W.  J.  Towne 765 

Concrete  Fence  Posts — L.  J.  Hotchkiss 766 

Discussion 774 

Report  of  Executive  Board 779 

Minutes  of  Meetings  of  the  Executive  Board 786 

Register  of  Attendance — ^Eighth  Convention 7^2 

Subject  Index 796 

Author  Index 804 

List  of  Publications 809 

Table  of  Contents 809 

Price  List 818 

PLATES 

The  Handling  of  Concrotc  in  the  Construction  of  the  Panama  Canal- 
Williamson. 

I.     Fig.     1. — Plan  and  Cross-section  Gatun  Locks 328 

II.     Fig.    2.— Concrete  Handling  Plant,  Gatun  Locks 328 

Fig.     3.— Wall  Forms,  Gatun  Locks 328 

III.  Fig.     6. — (>)ncrcte  Handling  Plant,  Mirafloroa  Ix)cks 340 

IV.  Fig.     7. — Details,  C>)ncretc  Handling  Plant,  Miraflores  Locks.    .  .   342 
V.     Fig.  10. — Forms  for  Wall,  Pedro  Miguel  and  Miraflores  I>ocks.  . .  .   344 

VI.     Fig.  11.— Handling  Plant,  Pedro  Miguel  I^cks 346 

VII.    Fig.  13. — Material  Handling  Cranes,  Pedro  Miguel  Ivocks 346 


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LIST  OF  OFFICERS 


OF 


THE  NATIONAL  ASSOCIATION  OF  CEMENT  USERS 

1912. 


PRESIDENT. 

RICHARD  L.  HUMPHREY. 


FIRST  VICE-PRESIDENT. 

EDWARD  D.  BOYER. 


SECOND  VICE-PRESIDENT. 

ARTHUR  N.  TALBOT. 


THIRD   VICE-PRESIDENT. 

EDWARD  S.  LARNED. 


FOURTH   VICE-PRESIDENT. 

IRA  H.  WOOLSON. 


SECRETARY. 

EDWARD  E.  KRAUSS. 


TREASURER. 

HENRY  C.  TURNER. 


SECTIONAL   VICE-PRESIDENTS. 
(See  page  7.) 


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SECTIONAL  COMMITTEES. 

(The  Chainnen  are  Vice-Presidents  of  the  Association.) 


BUILDING  BLOCKS  AND  CEMENT  PRODUCTS. 
P.  S.  Hudson,  Chairman, 

C.  K.   ABPy  ROBERT  V.  HAYUK, 

P.  H.   ATWOOD,  CHARLES  D.  WATSON. 

EXHIBITION. 
H.  S.  DoTLB,  Chairman, 

B.  F.   AFFI4ECK,  W.  J.  ROSBBERRT,   JR., 

W.   H.   BURKE,  P.   AUSTIN  TOMES. 

FIKEPROOFING. 
Rudolph  P.  Miller,  Chairman, 

EDWIN  CLARK,  JOHN  STEPHEN  SEWELL, 

W.   C.   ROBINSON,  IRA  H.  WOOLSON. 

INSURANCE. 
William  H.  Ham,  Chairman, 

A.   L.  JOHNSON,  F.  W.  MOSES, 

W.   H.   MERRILL,  J.  P.   H.  PERRY. 

MEASURING  CONCRETE. 
Robert  A.  Cummings,  Chairman. 

L.  H.   ALLEN,  CHARLES  DERLETH,   JR., 

ROBERT  ANDERSON,  THOMAS  M.  VINTON. 

NOMENCLATURE. 
Peter  Gillespie,  Chairman, 

E.  p.   GOODRICH,  F.  B.  TURNEAURE, 

E.  J.   MEHREN,  FRANK  C.  WIGHT. 

REINFORCED  CONCRETE  AND  BUILDING  LAWS. 
Alfred  E.  Lindau,  Chairman, 

W.  p.  ANDERSON,  ARTHX7R  N.  TALBOT, 

E.  J.   MOORE,  8ANF0RD  B.  THOMPSON. 

ROADWAYS,  SIDEWALKS  AND  FLOORS. 
C.  W.  BoYNTON,  Chairman. 

A.   G.  BIRNIE,  C.   R.   MILLER, 

i,  B.  LANDFPXD,  A.  B.  SN0DGRAB8, 

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Sectional  Committees. 


SPECIFICATIONS  AND   METHODS  OF  TESTS  P'OR  CONCRETE 

MATERIALS. 

Sanpord  E.  Thompson",  Chairman. 

CLOYD   M.    CHAPMAN,  RUSSELL   8.    GRBENMAN, 

WILLIAM   B.    FULLER,  ARTHUR   N.    TALBOT. 

TREATMENT  OF  CONCRETE  SURFACES. 
Leonard  C.  Wason,  Chairman. 

CLOYD   M.    CHAPMAN,  EMILE    O.    PERROT, 

ALFRED  HOPKINS,  H.   H.   QUIMBY. 

EDUCATION. 

Logan  Waller  Page,  Chairman. 
Percy  H.  Wilson,  Secretary. 
A.  C.  True.  Morris  Mbtcalf. 

William  G.  Hartranft.  A.  Moyer. 

W.  A.  Holman.  J.  P.  H.  Perry. 


Agricultural  Experiment  Stations. 


Alabama — J.  F.  Duogar. 
Arizona — Representative  not  yet 

appointed. 
Arkansas — Martin  Nelson. 
California — LeRoy  Anderson. 
Colorodo — Alvin  Keyser. 
Connecticut — Charles  A.  Wheeler. 
Delaware — Harry  Hayward. 
Florida — ^J.  J.  Vernon. 
Georgia — LeRoy  C.  Hart. 
Idaho — W.  L.  Carlyle. 
Illinois — E.  A.  White. 
Indiana — A.  T.  Wiancke. 
Iowa — J.  B.  Davidson. 
fiansas — W.  W.  Jardjnk. 
Kentucky — M.  A.  Scovell. 
I^uisiana — W.  R.  Dodson. 
Maine — George  E.  Summons. 
Maryland — W.  T.  L.  Taliaferro. 
Massachusetts — Wiluam  D.  Hurd. 
Michigan — R.  S.  Shaw. 
Minnesota — John  T.  Stewart. 
Mississippi — W.  L.  Hutchinson. 
Missouri — F.  B.  Mumford. 
Montana — H.  B.  Bonebright. 


Nebraska — L.  W.  Chase. 
Nevada — Representative  not  yet 

appointed. 
New  Hampshire — F.  W.  Taylor. 
New  Jersey — ^J.  G.  Lipman. 
Neiv  Mexico — F.  L.  Bixby. 
New  York—n.  W.  Riley. 
North  Carolina — C.  L.  Newman. 
North  Dakota — ^J.  H.  Shepperd. 
Ohio — H.  C.  Hamsower. 
Oklahoma — O.  O.  Churchill. 
Oregon — H.  D.  Scudder. 
Pennsylmnia — Frank  D.  Gardener. 
Rhode  Island — G.  E,  Adams, 
South  Carolina — W.  R,  Perkjns. 
South  Dakota — A,  N.  Hume. 
Tenntissee — C,  A.  Moores, 
Texas — S.  S.  McMjllant. 
IJtah—F,  S.  Harris. 
Vermont — J.  W.  Elliot. 
Virginia — H.  L.  Price. 
Washington — O.  L.  Waller. 
West  Virginia — I.  S.  Cook. 
Wisconsin — Charles  A.  Ocock. 
Wyoming — J.  C.  F|tterer. 


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PAST  OFFICERS. 


President. 


1905        John  P.  Given. 

(Presiding  Officer  First  Convention.) 

1905-11  Richard  L.  Humphrey. 


First  Vice-President. 


1905  a.  l.  goetzmann. 
1906-9  Merrill  Watson. 
1909-11  Edward  D.  Boyer. 


Second  Vice-President. 


1905-6    John  H.  Fellows. 
1907-10  M.  S.  Daniels. 
1911        Arthur  N.  Talbot. 


Third  Vice-President. 


1905        H.  C.  QuiNN. 
1906-7    0.  U.  Miracle. 
1908        S.  B.  Newberry. 
1909-11  E.  S.  Larned. 


Fourth  Vice-President. 


1905-7    A.  Monsted. 
1908-9    George  C.  Walters. 
1909-10  F.  A.  NoRRis. 
1911        Ira  H.  Woolsen. 


Treasurer. 


1905        A.  S.  J.  Gammon. 
1906^11  H.  C.  Turner. 


Secretary. 


1905-6  Charles  C.  Brown. 

1907  W.  W.  Curtis. 

1908-9  George  C.  Wright. 

1910  Edward  E.  Krauss  (Acting) 

1911  Edward  E.  Krauss, 


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CHARTER 

OF 

THE  NATIONAL  ASSOCIATION  OF  CEMENT  USERS. 


KNOW  ALL  MBN  BY  THBSB  PRBSBNTS,  That  we,  the  under- 
signed, all  of  whom  are  citizens  of  the  United  States,  and  a  majority  of 
whom  are  residents  of  the  District  of  Columbia,  have  associated  our- 
selves together  for  the  purpose  hereinafter  set  forth  and  desiring  that 
we  may  be  incorporated  as  an  Association  under  sub-chapter  three  (3)  of 
the  Incorporation  Laws  of  the  District  of  Columbia,  as  provided  in  the 
Code  of  Law  of  the  District  of  Columbia,  enacted  by  Congress  and  ap- 
proved by  the  President  of  the  United  States,  do  hereby  certify: 

/•  Nmm€.  The  name  of  the  proposed  corporation  is  "The  National 
Association  of  Cement  Users." 

2.  Term  oi  Bxiateace.  The  existence  of  the  said  corporation  shall 
be  perpetual. 

3.  OtiectMm  The  particular  business  and  objects  of  the  said  corpora- 
tion shall  be  to  disseminate  information  and  experience  upon  and  to 
promote  the  best  methods  to  be  employed  in  the  various  uses  of  cement  by 
means  of  convention,  the  reading  and  discussion  of  papers  upon  materials 
of  a  cement  nature  and  their  uses,  by  social  and  friendly  intercourse  at 
such  conventions,  the  exhibition  and  study  of  materials,  machinery  and 
methods  and  to  circulate  among  its  members  by  means  of  publications  the 
information  thus  obtained. 

4.  iacorpormton.  The  number  of  its  managers  for  the  first  year 
shall  be  fifteen. 

la  WItaeMB  Whereof,  we  have  hereunto  set  our  hands  and  seals  this 
fourteenth  day  of  December,  A.  D.  1906. 

RICHARD  L.  HUMPHREY,  (Seal) 

JOHN  STEPHEN  SEWELL,  (Seal) 

S.  S.  VOORHEES.  (Seal) 

Office  of  Recorder  of  Deeds, 
District  of  Columbia. 
This  is  to  certify  that  the  foregoing  is  a  true  and  verified  copy  of  a 
Certificate  of  Incorporation,  and  of  the  whole  of  such  Certificate  as  re- 
ceived for  record  in  this  office  at  9 :  49  A.  m.,  the  19th  day  of  December, 
A.  D.  1906. 

In  testimony  whereof  I  have  hereunto  set  my  hand  and  affixed  the 
teal  of  this  office,  this  20th  day  of  December,  A.  D.  1906. 
(Signed)  R.  W.  DUTTON, 

Deputy  Recorder  of  Deeds, 

LHstrict  of  Columbia 

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BY-LAWS. 
Article  I. 

MEMBERS. 

Section  1.  Any  person  engaged  in  the  construction  or 
maintenance  of  work  in  which  cement  is  used,  or  qualified  by 
business  relations  or  practical  experience  to  co-operate  in  the  pur- 
poses of  this  Association,  or  engaged  in  the  manufacture  or  sale 
of  machinery  or  supplies  for  cement  users,  or  a  man  who  has 
attained  eminence  in  the  field  of  engineering,  architecture  or 
applied  science,  is  eligible  for  membership. 

Sec.  2.  A  firm  or  company  shall  be  treated  as  a  single  mem- 
ber. 

Sec.  3.  Any  member  contributing  annually  twenty  or  more 
dollars  in  addition  to  the  regular  dues  shall  be  designated  and 
listed  as  a  Contributing  Member. 

Sec.  4.  Application  for  menibership  shall  be  made  to  the 
Secretary  on  a  form  prescribed  by  the  Board  of  Direction.  The 
Secretary  shall  submit  monthly  or  oftener  if  necessary  to  each 
member  of  the  Board  of  Direction  for  letter  ballot  a  list  of  all 
applicants  for  membership  on  hand  at  that  time  with  a  statement 
of  the  qualifications,  and  a  two-thirds  majority  of  the  members  of 
the  Board  shall  be  necessary  to  an  election. 

Applicants  for  membership  shall  be  qualified  upon  notification 
of  election  by  the  Secretary  by  the  payment  of  the  annual  dues, 
and  unless  these  dues  are  paid  within  60  days  thereafter  the  elec- 
tion shall  become  void.  An  extract  of  the  By-Laws  relating  to 
dues  shall  accompany  the  notice  of  election. 

Sec.  5.  Resignations  from  membership  must  be  presented 
in  writing  to  the  Secretary  on  or  before  the  close  of  the  fiscal  year 
^pd  shall  be  acceptable  provided  the  dues  are  paid  for  that  year, 


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12  By-Laws. 

Article  II. 

OFFICERS. 

Section  1.  The  officers  shall  be  the  President,  two  Vice- 
Presidents,  six  Directors  (one  from  each  geographical  district), 
the  Secretary  and  the  Treasurer,  who,  with  the  five  latest  living 
Past-Presidents,  who  continue  to  be  members,  shall  constitute 
the  Board  of  Direction. 

Sec.  2.  The  Board  of  Direction  shall,  from  time  to  time, 
divide  the  territory  occupied  by  the  membership  into  six  geographi- 
cal districts,  to  be  designated  by  numbers. 

Sec.  3.  The  terms  of  office  of  the  President,  Secretary  and 
Treasurer  shall  be  one  year;  of  the  Vice-Presidents  and  the  Direct- 
ors, two  years.  Provided,  however,  that  at  the  first  election  after 
the  adoption  of  this  By-Law,  a  President,  one  Vice-President, 
three  Directors  and  a  Treasurer  shall  be  elected  to  serve  for  one 
year  only,  and  one  Vice-President  and  three  Directors  for  two 
years;  provided,  also,  that  after  the  first  election  a  President,  one 
Vice-President,  three  Directors  and  a  Treasurer  shall  be  elected 
annually. 

The  term  of  each  officer  shall  begin  at  the  close  of  the  Annual 
Convention  at  which  such  officer  is  elected,  and  shall  continue  for 
the  period  above  named  or  until  a  successor  is  duly  elected. 

A  vacancy  in  the  office  of  President  shall  be  filled  by  the  senior 
Vice-President.  A  vacancy  in  the  office  of  Vice-President  shall 
be  filled  by  the  senior  Director. 

Seniority  between  persoas  holding  similar  offices  shall  be 
determined  by  priority  of  election  to  the  office,  and  when  these 
dates  are  the  same,  by  priority  of  admission  to  membership; 
and  when  the  latter  dates  are  identical,  the  selection  shall  be  made 
by  lot.  In  case  of  the  disability  or  neglect  in  the  performance  of 
his  duty,  of  any  officer  of  this  Association,  the  Board  of  Direction 
shall  have  power  to  declare  the  office  vacant.  Vacancies  in  any 
office  for  the  unexpired  term  shall  be  filled  by  the  Board  of  Direc- 
tion, except  as  provided  above. 

Sec.  4.  The  Board  of  Direction  shall  appoint  the  Secretary; 
it  shall  create  such  special  committees  as  may  be  deemed  desirable 
for  the  purpose  of  preparing  recommended  practice  and  standards 
concerning  the  proper  use  of  cement  for  consideration  by  the 


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By-Laws.  13 

Association,  and  shall  appoint  a  chairman  for  each  committee. 
Four  or  more  additional  members  on  each  special  committee 
shall  be  appointed  by  the  President,  in  consultation  with  the 
Chainnan. 

Sec.  5.  It  shall  be  the  duty  of  the  Board  of  Direction  to 
audit  the  accounts  of  the  Secretary  and  the  Treasurer  before  each 
annual  convention. 

Sec.  6.  The  Board  of  Direction  shall  appoint  a  Committee 
on  Nomination  of  Officers  and  a  Committee  on  Resolutions,  to  be 
announced  by  the  President  at  the  first  regular  session  of  the 
annual  convention. 

Sec.  7.  There  shall  be  an  Executive  Committee  of  the 
Board  of  Direction,  consisting  of  the  President,  the  Secretary,  the 
Treasurer  and  two  of  its  members,  appointed  by  the  Board  of 
Direction. 

Sec.  8.  The  Executive  Committee  shall  manage  the  affairs 
of  the  Association  during  the  interim  between  the  meetings  of 
the  Board  of  Direction. 

Sec.  9.  The  President  shall  have  general  supervision  of  the 
affairs  of  the  Association.  He  shall  preside  at  the  Annual  Con- 
vention, at  the  meetings  of  the  Board  of  Direction  and  the  Execu- 
tive Committee,  and  shall  be  ex-officio  member  of  all  conmiittees. 

The  Vice-Presidents  in  order  of  seniority  shall  discharge  the 
duties  of  the  President  in  his  absence. 

Sec.  10.  The  Secretary  shall  perform  such  duties  and  fur- 
nish such  bond  as  may  be  determined  by  the  Board  of  Direction. 

Sec.  11.  The  Treasurer  shall  be  the  custodian  of  the  funds 
of  the  Association,  shall  disburse  the  same  in  the  manner  prescribed 
and  shall  furnish  bond  in  such  sum  as  the  Board  of  Direction  may 
determine. 

Sec.  12.  The  Secretary  shall  receive  such  salary  as  may  be 
fixed  by  the  Board  of  Direction. 

Article  III. 

MEETINGS. 

Section  1.  The  Association  shall  meet  annually.  The  time 
and  place  shall  be  fixed  by  the  Board  of  Direction  and  notice  of 
this  action  shall  be  mailed  to  all  members  at  least  thirty  days 
previous  to  the  date  of  the  Convention. 


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14  bT-tiAW&. 

Sec.  2.  The  Board  of  Direction  shall  meet  immediately 
after  the  Convention  at  which  it  was  elected,  effect  organization 
and  transact  such  business  as  may  be  necessary. 

Sec.  3.  The  Board  of  Direction  shall  meet  at  least  twice 
each  year.  The  time  and  place  to  be  fixed  by  the  Executive  Com- 
mittee. 

Sec.  4.  A  majority  of  the  members  shall  constitute  a 
quorum  for  meetings  of  the  Board  of  Direction  and  of  the  Executive 
Committee. 

Article  IV. 

DUES. 

Section  1  The  fiscal  year  shall  commence  on  the  first 
of  July  and  all  dues  shall  be  payable  in  advance. 

Sec.  2.  The  annual  dues  of  each  member  shall  be  five  dollars 
($5.00). 

Sec.  3.  Any  person  elected  after  six  months  of  any  fiscal 
year  shall  have  expired,  need  pay  only  one-half  of  the  amount 
of  dues  for  that  fiscal  year;  but  he  shall  not  be  entitled  to  a  copy 
of  the  Proceedings  of  that  year. 

Sec.  4.  A  member  whose  dues  remain  unpaid  for  a  period  of 
three  months  shall  forfeit  the  privilege  of  membership  and  shall 
be  officially  notified  to  this  effect  by  the  Secretary,  and  if  these 
dues  are  not  paid  within  thirty  days  thereafter  his  name  shall  be 
stricken  from  the  list  of  members.  Members  may  be  reinstated 
upon  the  payment  of  all  indebtedness  against  them  upon  the  books 
of  the  Association. 

Article  V. 

RECOBfBfENDED  PRACTICE  AND   SPECIFICATIONS. 

Section  1.  Proposed  Recommended  Practice  and  Specifica- 
tions to  be  submitted  to  the  Association  must  be  mailed  to  the 
members  at  least  thirty  days  prior  to  the  Annual  Convention,  and 
as  there  amended  and  approved,  passed  to  letter  ballot,  which  shall 
be  canvassed  within  sixty  days  thereafter,  such  Recommended 
Practice  and  Specifications  shall  be  considered  adopted  unless  at 
least  ten  per  cent,  of  the  total  membership  shall  vote  in  the 
negative. 


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Akticle  VI. 

AMENDMENT 

Section  1.  Amendments  to  these  By-Laws,  signed  by  at 
least  fifteen  members,  must  be  presented  in  writing  to  the  Board  of 
Direction  ninety  days  before  the  Annual  Convention  and  shall  be 
printed  in  the  notice  of  the  Annual  Convention.  These  amend- 
ments may  be  discussed  and  amended  at  the  Annual  Convention 
and  passed  to  letter  ballot  by  a  two-thirds  vote  of  those  present. 
Two-thirds  of  the  votes  cast  by  letter  ballot  shall  be  necessary 
for  their  adoption. 


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SUMMARY  OF  THE  PROCEEDINGS  OF  THE  EIGHTH 
ANNUAL  CONVENTION. 


First  Session,  Monday,  March  U,  1912,  8  p.  m. 

The  Convention  was  called  to  order  by  the  President,  Richard 
L.  Humphrey. 

John  Lyle  Harrington,  Past  President,  Engineers'  Club  of 
Kansas  City,  delivered  an  address  of  welcome  on  behalf  of  the 
Engineering  Interests  as  follows: 

In  the  dark  ages  of  industry  which  extended  well  into  the  last  century, 
it  was  the  custom  for  every  member  of  a  craft,  trade  or  profession  to  guard 
jealously  and  to  keep  closely  secret  every  item  of  knowledge  he  or  his  associates 
had,  in  order  to  secure  to  himself  the  whole  advantage  of  it.  In  addition  to 
patenting  an  invention,  it  was  common  to  keep  secret  every  possible  detail 
of  the  processes  employed,  and  many  businesses  were  based  wholly  upon 
secret  formulae  which  were  closely  held  by  members  of  a  firm  or  family,  often 
handed  down  from  father  to  son,  and  the  utmost  precautions  were  taken  to 
ensure  that  employees  and  even  associates,  as  well  as  competitors,  actual  and 
potential,  should  be  kept  in  ignorance  of  the  methods  employed  or  discoveries 
made.  Even  up  to  the  present  day  it  is  dangerous  in  some  e.stablishments 
for  an  employee  to  ask  too  many  questions  regarding  the  methods  of  manu- 
facture or  materials  he  employs  in  his  work,  and  in  certain  lines  of  manufacture 
a  considerable  remnant  of  this  old  secrecy  remains.  Here  and  there  the 
possessor  of  a  formula  has,  like  the  old  alchemist,  at  the  right  moment  dropped 
his  fluid  into  a  molten  metal  or  added  his  mite  to  the  production  of  important 
materials  and  kept  the  secret  and  profits  thereof  to  himself. 

But  early  in  the  last  century  the  civil  engineers  of  Great  Britain  met  and 
formed  an  institute  for  the  purpose  of  disseminating  the  knowledge  acquired 
by  its  individual  members;  and  in  the  latter  half  of  the  century  the  engineers 
of  this  country  came  to  appreciate  the  advantages  of  co-operation.  The 
first  such  organizations  were  few  in  number  and  comprehensive  in  scope, 
but  gradually  important  groups  working  in  special  lines  came  to  feel  that  the 
interests  of  the  broad  general  organization  were  too  varied  to  permit  adequate 
consideration  of  the  matters  which  specially  occupied  their  attention  and  so 
they  split  off  and  organized  societies  of  more  limited  .scope.  With  the  enor- 
mous development  of  industries  based  on  the  appliinl  sciences  special  interests 
so  increased  in  value  and  importance  that  the  benefits  to  be  derived  from  close 
association  and  active  discussions  of  men  engaged  in  them  came  to  be  generally 
understood,  and  group  organizations  grew  apace. 

(10) 


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Summary  of  Proceedings,  Eighth  Convention.         17 

In  the  course  of  time,  manufacturers  began  to  understand  that  by  keep- 
ing to  themselves  knowledge  of  their  s|x;cialities  they  encouraged  like  action 
on  the  part  of  their  competitors — and  each  member  of  that  branch  of  industrj' 
developed  internally  only.  This  limited  the  development  of  all  and  circum- 
scribed the  field  of  the  industry.  Gradually  it  became  evident  that  the 
advancement  of  the  industry  resulting  from  the  dissemination  of  knowledge 
of  it  among  those  engaged  in  it  more  than  compensated  for  the  advantage 
secured  even  by  the  most  successful  operation  under  the  secret  methods.  As 
soon  as  this  fact  came  to  be  fully  realized  the  organization  of  special  societies 
for  special  purposes  multiplied  rapidly.  They  reacted  upon  the  industries 
and  the  accomplishments  of  one  man  so  pointed  out  possibilities  and  so 
stimulated  others  that  development  has  increased  in  geometric  ratio. 

Among  these  later  organizations  developed  to  special  interests,  the 
National  Association  of  Cement  Users  has  come  to  occupy  an  important 
place. 

Cement  in  some  form  has  been  in  use  for  many  centuries,  so  many  that 
its  origin  is  lost  in  antiquity;  but  the  development  of  Portland  cement  and 
the  industries  and  types  of  construction  dependent  upon  its  use  are  of  com- 
paratively recent  date.  It  is  hard  to  believe  that  less  than  twenty  years  ago 
Congress  gravely  questioned  the  existence  in  this  country  of  materials  essential 
to  the  manufacture  of  first-class  Portland  cement,  and  debated  whether,  in 
view  of  that  condition,  it  would  be  justifiable  to  impose  so  much  duty  on 
imported  cement  as  would  induce  its  manufacture  in  this  country.  Yet  hist 
year  we  produced  nearly  78,(XX),(XX)  barrels,  which,  at  the  existing  low  price 
prevailing,  brought  nearly  $(>8,(XX),(XX)  at  the  mills,  and  the  value  of  con- 
structions in  which  it  wjis  used  probably  reached  nearly  $500,000,000. 

It  is  well,  therefore,  that  the  users  of  cement,  the  men  who  are  respon- 
sible for  construction  of  cement  and  concrete  work  worth  one-half  billion 
dollars  per  annum,  should  organize  themselves  into  an  association  and  meet 
to  advance  their  special  interests  by  the  discussion  of  the  work  they  are  doing 
and  the  experiences  they  have  gained.  And  while  it  is  natural  and  right  that 
interest  and  enthusiasm  for  their  work  should  lead  chiefly  to  the  exposition 
of  the  successes  achieved,  it  is  quite  as  important  that  the  defects  found  in  the 
materials,  in  the  constructions  and  in  the  methods  employed  should  be 
exposed  and  discussed,  for  we  learn  as  much — often  more,  if  we  are  wise — 
from  our  failures  as  from  our  successes.  And  it  is  important  that  the  limita- 
tions of  materials  and  their  uses  be  fully  understood  and  bad  results  thus 
guarded  against,  and  the  character  of  the  practices  on  th<i  whole  thus  improved. 
The  effort  to  meet  the  ever-pressing  demand  for  cheap  construction  leads  to 
many  failures  and  to  much  consequent  damage  to  the  industry.  To  increase 
the  stresses  or  reduce  the  quality  of  concrete  in  order  to  enable  it  to  compare 
favorably  with  wood  in  first  cost  is  an  unwarranted,  but  far  too  common 
practice.  If  in  any  instance  its  many  superior  qualities  do  not  justify  the 
greater  expenditure  for  good  concrete  safely  stressed,  then  the  cheaper  mate- 
rials should  be  employed.  Wilful,  foolhardy  rLsks  are  responsible  for  some  of 
the  failures,  but  ignorance  of  all  conditions  governing  concrete  construction 


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18         Summary  op  t*ROCEia)iNGS,  Eighth  ConvenHok. 

is  by  far  the  larger  factor,  and  it  is  the  duty  and  purpose  of  this  organization 
to  expose  bad  construction  as  it  is  to  urge  good  methods  and  good  workmanship. 
Concrete  construction  is  peculiarly  liable  to  failure  through  both  ignorance 
and  carelessness.  Through  ignorance  because  its  use  in  the  simpler  tjrpes  of 
construction  leads  men  to  believe  its  employment  universally  simple;  through 
carelessness  because  it  is  so  amenable  to  the  employment  of  unskilled  labor 
which  needs,  but  does  not  always  receive,  thorough  and  careful  supervision. 
I  well  remember  the  county  engineer  who  was  confident  he  had  made  all  the 
plans  necessary  for  the  construction  of  a  reinforced  concrete  bridge  when  he 
had  made  a  picture  on  which  he  had  given  general  dimensions  and  shown  the 
location  of  some  reinforcement. 

Failure  to  recognize  the  need  of  careful  inspection  of  materials  and  super- 
vision of  workmanship  is  perhaps  responsible  for  the  larger  portion  of  failures 
of  concrete  structures.  Steel  is  manufactured  by  skilled  men  working  under 
able  superintendence  and  so  continuously  employed  that  they  come  to  under- 
stand the  processes  thoroughly;  whereas  concrete  is  conmionly  manufactured 
by  an  itinerant,  common  laborer  and  often  directed  by  a  foreman  whose 
only  qualification  is  his  ability  to  handle  men.  Constructions  of  wood, 
brick  or  stone  may  be  fairly  well  inspected  at  any  stage  or  after  completion, 
but  the  character  of  concrete  construction  may  not  be  determined  until 
after  the  forms  are  removed,  and  remedying  defects  then  disclosed  is  always 
difficult,  often  impossible.  Too  early  removal  of  the  forms,  thus  placing  upon 
the  concrete  stresses  which  it  is  yet  unfitted  to  bear;  carelessness  and  imwise 
placing  of  reinforcement;  inadequate  provision  for  expansion  and  contrac- 
tion due  to  changes  of  temperature;  weak  and  leaky  forms;  inadequate 
tamping;  loose  methods  of  depositing  concrete,  both  in  air  and  under  water; 
excessive  dependence  in  designing  upon  empirical  methods  and  fallacious 
load  tests;  these  and  many  other  difficulties  must  be  guarded  against  and 
overcome.  Much  disappointment  is  certainly  in  store  for  the  owners  of 
staff  and  concrete  buildings  who  have  not  fully  appreciated  the  difficulties 
in  securing  construction  which  will  resist  the  weather.  There  are  many  other 
difficulties  which  must  be  guarded  against  and  overcome. 

As  the  use  of  concrete  becomes  more  general,  more  attention  is  given  to 
the  sightliness  of  structures  built  of  it,  but  too  often  the  efforts  in  this  line 
are  misdirected.  It  should  be  clearly  recognized  that  this  material  is  capable 
of  excellent  treatment  peculiar  to  itself,  and  that  it  is  an  error  to  try  to 
make  it  resemble  other  materials.  The  old  Spanish  structures  of  southwestern 
states  and  Mexico  are  beautiful  because  they  are  true.  They  were  designed 
frankly  to  be  built  of  concrete  and  have  forms  and  finish  suitable  for  that 
material.  It  may  be  that  with  the  wider  use  and  fuller  development  of  con- 
crete construction  we  may  improve  upon  the  work  of  these  Spaniards,  but 
we  have  not  by  any  means  equalled  it  as  yet.  The  endeavor  to  meet  the  needs 
of  the  material  has  too  frequently  led  to  the  adoption  of  extreme  and  grotesque 
forms  and  finishes  which  soon  weary  or  offend. 

We  are  gradually  improving  the  finish  of  our  concrete  structures  and 
recent  work  in  this  line  is  especially  promising,  but  much  remains  to  be  done 
both  for  the  appearance  and  for  the  weathering  quality  of  concrete  and  staff 


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SUMMART  OP  PROCEEBtNGft,   ElGHTH  CoNVfcNTtOI^.  19 

^surfaces.  Good  finish  adds  to  the  cost,  but  the  extra  expense  is  surely  jus- 
tified. 

The  gfeat  advantages  of  concrete,  durability,  loW  cost  as  compared  with 
other  equally  durable  materials,  ease  of  handling,  ease  of  molding  to  the  forms 
desired,  resistance  to  fire,  strength  and  homogeneity)  adaptability  to  many 
uses,  both  with  and  without  reinforcement,  resistance  to  acids  and  decay^ 
attractiveness  of  appearance  and  the  wide  distribution  of  its  constituent 
materials,  improvements  in  methods  of  construction,  and  the  steadily 
increased  scarcity  and  cost  of  good  timber  ensure  continual  increase  in  the 
use  of  concrete.  But  perhaps  the  greatest  argument  in  favor  of  fireproof 
concrete  buildings  is  the  enormous  fire  loss  this  country  sustains  through 
the 'excessive  use  of  wood  and  the  equally  great  cost  of  fire  insurance.  Our 
losses  by  fire  have  become  a  national  disgrace. 

The  influence  of  this  Association  should  be  very  great  in  combating  the 
tendency  of  some  constructors  to  secure  business  and  profit  by  reducing  the 
quality  of  work.  This  course  surely  militates  against  the  interest  of  cement 
users  as  a  whole  and  it  brings  their  work  as  a  whole  into  disrepute.  This  was 
clearly  exemplified  recently  at  Los  Angeles  where  the  city  engineer  recom- 
mended creosoted  instead  of  reinforced  concrete  piles  for  dock  construction 
and  was  able  to  justify  his  position  by  citing  about  a  dozen  failures  of  docks 
which  were  supported  on  reinforced  concrete  piles.  And  generally  speaking, 
any  improper  use  of  the  material  of  construction  affects  adversely  the  inter- 
ests of  all  who  engage  in  the  use  of  that  material.  There  is,  therefore,  a  large 
opportunity  for  this  Association  to  benefit  greatly  the  interests  of  its  members 
and  to  benefit  the  country  at  large  by  compelling  a  high  standard  of  ability 
and  integrity  among  cement  users. 

It  is  thus  apparent  that  this  Association  has  met  to  deal  with  subjects 
of  the  largest  consequence  and  the  effects  of  its  discussions  will  be  to  improve 
throughout  this  country  and  other  countries  the  practices  of  concrete  design 
and  construction.  The  work  of  this  Association  is,  in  no  inconsiderable 
measure,  the  work  of  the  Engineer.  He  shares  largely  in  the  work  and  the 
responsibilities  and  the  benefits  of  this  convention;  hence  it  is  with  pleasure 
and  cordial  good  will  that  on  behalf  of  the  Engineers  of  Kansas  City,  I  extend 
a  hearty  welcome  to  the  National  Association  of  Cement  Users. 

An  address  of  welcome  on  behalf  of  the  Concrete  Interests 
was  made  by  F.  W.  Pratt,  President  of  the  Union  Bridge  and 
Terminal  Railroad  Company. 

The  President  responded: 

The  Convention  has  this  year  been  fortunate  in  haying  two  eminent 
engineers  express  thoughts  that  will  be  of  good  service  to  the  Association 
in  its  future  work.  I  am  sure  that  you  all  join  me  in  reciprocating  the 
good  wishes  which  Mr.  Harrington  and  Mr.  Pratt  have  extended  to  us,  and 
in  the  hope  that  our  deliberations  may  prove  of  interest  and  value. 


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20         Summary  of  t^ROckEDiNGs,  Eighth  Convention. 

The  following  committees  of  the  Convention,  appointed  by 
the  Executive  Board,  were  announced  by  the  President: 

Committee  on  Nomination  of  Officers: 

E.  J.  Moore,  Chairman^  New  York,  N.  Y. 
D.  A.  Abrams,  Ames,  Iowa. 

John  L.  Conzelman,  St.  Ix)uis,  Mo. 

B.  F.  Lippold,  Chicago,  III. 

Ij.  T.  Sunderland,  KanHa.s  CMty,  Mo. 

Committee  on  Resolutions: 

Rudolph  P.  Miller,  Chairman,  New  York,  N.  Y. 
P.  n.  Bates,  PittsburKh,  Pa. 
Allen  Brett,  New  York,  N.  Y. 

F.  L.  Williamson,  Kansjus  C'ity,  Mo. 
Perry  H.  Wilson,  Philadelphia,  Pa. 

A  paper  on  *'Th(»  Use  of  Reinforced  Concrete  in  Hypochlorite 
Water  Purification  Works"  was  read  by  Walter  M.  Ooss. 

(leorge  E.  Tebbetts  presented  a  paper  on  *'The  Use  of  Con- 
crete in  the  New  Union  Station  at  Kansas  City,  Mo.,"  which 
wjis  followed  l)y  a  discussion. 

The  meeting  adjourncMl  until  Tuesday  at  10.30  A.  m. 


Tuesday,  March  12,  1912,  10.00  a.  m. 

Meeting  of  the  Sections  on  Mcnisuring  ('oncrete.  Nomen- 
clature, and  Specifications  and  Methods  of  Tests  for  Concrete 
Materials. 

President  Richard  L.  Humphrey  in  the  chair. 

The  meeting  took  the  form  of  a  discussion  on  the  deposition 
of  mortar  with  compressed  air,  its  effectiveness  and  various 
methods  of  application. 


Second  Session,  Tuesday,  March  12,  1912,  10.30  a.  m. 

President  Richard  L.  Humphrey  in  the  chair. 

The  report  of  the  Committee  on  Specifications  and  Methods 
of  Tests  for  ('oncrete  Materials  was,  in  the  absence  of  the  Chair- 
man, Sanford  E.  Thompson,  presented  by  Cloyd  M.  Chapman. 

Wm.  M.  Kinney  read  a  paper  on  "Aggregates  for  Concrete," 


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Summary  of  Proceedings,  Eighth  Convention.         21 

which  was  followed  by  a  Topical  Discussion  on  Concrete  Aggre- 
gates. 

In  the  absence  in  Europe  of  the  Chairman,  Robert  A. 
Cummings,  Edw.  D.  Boyer  presented  the  report  of  the  Com- 
mittee on  Measuring  Concrete,  which  was  followed  by  a  dis- 
cussion. The  Proposed  Standard  Method  of  Measuring  Concrete 
was  referred  back  to  the  Committee,  with  instructions  for  a 
revision  in  the  light  of  the  discussion  and  report  at  the  next 
annual  Convention. 


Third  Session— Tuesday,  March  12,  1912,  8.00  p.  m. 

President  Richard  L.  Humphrey  in  the  chair. 
The  annual  address  of  the  President,  entitled  **The  Use  of 
Concrete  in  Eurojx*,*'  was  delivered  by  Richard  L.  Humphrey. 
The  following  papers  were  then  read  and  discussed: 

"The  Design  and  Construction  of  the  Hollow  Reinforced 
Concrete  Dam  of  the  Portland  Railway  Light  and 
Power  Company,"  by  Herman  V.  Schreiber. 

"Cement  Coatings  in  Color,''  by  F.  J.  Morse. 

The  report  of  the  Committee  on  Concrete  Surfaces  was 
presented  by  the  C'hairman,  L.  C.  Wason.  On  motion  the  pro- 
posed Standard  Method  for  Tests  of  Waterproofing  was  referred 
to  the  Committee  on  Specifications  and  Methods  of  Tests  for 
Concrete  Materials,  for  report.  Consideration  of  the  proposed 
Standard  Specification  for  Portland  Cement  Stucco  was  deferred 
imtil  a  later  session.  The  changes  in  the  last  general  report  of 
the  Committee  were  approved. 

The  report  of  the  Committee  on  Insurance  was,  in  the 
absence  of  the  Chairman,  Wm.  H.  Ham,  read  by  title. 

The  meeting  then  adjourned  until  Wednesday  at  9.30  a.  m. 


Fourth  Session — Wednesday,  March  13,  1912,  9.30  a.  m. 

President  Richard  L.  Humphrey  in  the  chair. 

In  the  absence  of  the  author,  Sanford  E.  Thompson,  the 
President  read  the  paper  entitled  "The  Practical  Design  of 
Reinforced  Concrete  Flat  Slabs." 


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22  SUMliART  OP  PROCEEDINGS;   ElGHTH  CONVENTION. 

The  report  of  the  Committee  on  Reinforced  Concrete  and 
Building  Laws  was  presented  by  the  Chairman,  Alfred  E.  Lindau, 
and  Arthur  N.  Talbot,  and  was  followed  by  a  discussion. 

The  President  then  presented  the  annual  report  of  the 
Executive  Board,  submitting  a  proposed  revision  of  the  By-Laws, 
which  were  amended  and  ordered  to  letter  ballot.  The  report 
was  approved. 

The  change  of  name  of  the  Association  was  discussed  and 
on  motion  the  matter  was  referred  to  the  Executive  Board,  with 
authority  to  effect  a  change  in  name  if  deemed  expedient  for  the 
best  interests  of  the  Association. 

The  Committee  on  Nomination  of  Officers  presented  the 
following  nominations,  which  were  unanimously  approved  and 
the  Secretary  instructed  to  cast  the  ballot  for  their  election: 

Presidenty  Richard  L.  Humphrey,  Philadelphia,  Pa. 
First  Vice-President,  Edward  D.  Boyer,  Catasauqua,  Pa. 
Second  Vice-President,  Arthur  N.  Talbot,  Urbana,  111. 
Third  Vice-President,  Edward  S.  Lamed,  Boston,  Ma«s. 
Fourth  Vice-President,  Ira  H.  Woolson,  New  York,  N.  Y. 
Treasurer,  Henry  C.  Turner,  New  York,  N.  Y. 

The  time  and  place  of  the  Ninth  Annual  Convention  was 
referred  to  the  Executive  Board  with  power  to  act. 
The  meeting  then  adjourned  imtil  3  p.  m. 


Fifth  Session — ^Wednesday,  March  13,  1912,  3.00  p.  m. 

President  Richard  L.  Humphrey  in  the  chair. 
The  following  papers  were  read  and  discussed: 

"The   Testing  of  Reinforced   Concrete   Buildings  under 

Load,"  by  W.  A.  Slater. 
"The  Design  of  Concrete  Flat  Slabs,"  by  Frank  J.  Tre- 
lease;  in  the  absence  of  the  author  read  by  Alfred  E. 
Lindau. 
"The  Present  Status  of  Unit  Construction,"  by  James  L. 
Darnell. 
In  the  absence  of  the  author,  Theodore  H.  Skinner,   the 
paper  on  "A  Fireproof  School  of  Concrete,"  was  read  by  title. 
The  meeting  then  adjourned  until  8.00  p.  m. 


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SUMMABT  OF  PROCEEDINGS,   ElGHTH  CONVENTION.  23 

Sixth  Session — ^Wednesday,  March  13,  1912,  8.00  p.  m. 

President  Richard  L.  Humphrey  in  the  chair. 

The  President  introduced  the  Honorable  Darius  A.  Brown, 
Mayor,  who  extended  an  address  of  welcome  to  Kansas  City  as 
follows: 

Mayor  Brown. — I  am  glad  of  the  opportunity  to  appear  before  you  and 
express  my  appreciation  of  the  fact  that  men  should  gather  together  in  this 
city  for  the  purpose  of  discussing  the  matters  which  have  brought  you  here. 
We  have  heard  about  the  Stone  Age,  the  Wooden  Age  and  the  Iron  Age,  and 
I  think  it  is  the  consensus  of  opinion  that  we  are  now  in  the  Concrete  Age 
and  that  all  of  the  improved  structures  are  coming  to  be  made  of  this  material. 
We  are  also  in  the  age  of  progress  and  advancement;  we  are  in  an  age  when 
people  have  adopted  the  idea  that  if  a  thing  is  worth  doing  at  all  it  is  worth 
doing  well  and  that  is  the  reason  why  in  every  branch  of  human  industry, 
in  business,  in  commerce,  in  the  sciences  and  in  the  professions,  they  gather 
together  periodically  for  the  purpose  of  discussing  the  ways  and  means  of  better 
doing  the  business  in  which  they  are  engaged. 

I  am  satisfied  that  the  result  of  your  deliberations  will  not  only  be  of 
benefit  to  you  in  your  particular  business  but  will  be  of  benefit  to  the  com- 
munity in  which  you  live  and  benefit  to  the  American  people  as  a  whole. 
I  hope  one  of  the  results  of  your  deliberations  will  be  that  the  use  of  concrete 
will  become  so  perfected  that  it  will  not  only  give  us  more  comfortable  build- 
ings and  better  and  more  ornamental  structures  but  will  decrease  the  cost  of 
those  materials  to  the  people;  because  that  is  one  of  the  great  problems  to  be 
solved. 

On  behalf  of  the  people  of  Kansas  City  I  want  to  extend  to  you  a  very 
cordial  welcome  and  trust  that  you  will  not  only  be  benefited  by  your  delibera- 
tons  but  that  you  will  have  some  pleasure  while  staying  in  our  city.  I  thank 
you. 

The  President  responded: 

I  am  sure  we  all  appreciate  the  welcome  that  has  been  extended  by  His 
Honor.  A  city  of  this  size  in  whose  immediate  vicinity  there  is  a  production 
of  Portland  cement  of  about  one-tenth  of  that  of  the  entire  country,  is  a 
good  place  in  which  to  hold  deliberations  of  this  character.  In  accepting 
the  hospitality  of  this  city  we  do  so  with  a  feeling  that  we  will  be  benefited. 
Our  conventions  have  been  held  heretofore  east  of  the  Mississippi  River, 
and  I  believe  that  the  mingling  of  the  eastern  and  western  ends  of  this 
great  country  cannot  help  but  be  beneficial  to  all.  I  know  you  will  join  me 
in  extending  to  Mayor  Brown  hearty  thanks  for  his  welcome. 

A  paper  on  "The  Use  of  Reinforced  Concrete  on  the  Wabash 
Railroad,"  was  presented  by  A,  0.  Cunningham, 


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24         Summary  of  Proceedings,  Eighth  Convention. 

The  report  of  the  Committee  on  Treatment  of  Concrete 
Surfaces  was  taken  up  and  on  motion  the  proposed  Standard 
Specification  for  Portland  Cement  Stucco  was  received  as  in- 
formation and  the  Committee  instructed  to  confer  with  other 
Associations,  in  order  to  reach  an  agreement  as  to  a  specifica- 
tion to  be  presented  at  the  next  Convention. 

The  following  papers  were  then  read  and  discussed: 

"The  Design  and  Construction  of  a  Reinforced  Concrete 
Dome,   220   Foot   Span,"   by  S.   J.   Trauer;    in  the 
absence  of  the  author  read  by  the  President. 
'*Tho  Design  of  Concrete  (irain  Elevators,"  by  E.  Ja'v 

Heidenreich. 
'*The  Suitability  of  Concrete  for  (liis  Holder  Tanks/'  by 
Herbert  W.   Alrich;    in  the  absence  of  the   author 
presented  by  the  President. 
"The  Necessity  of  Field  Tests  for  Concrete,"  by  Fritz  E. 
Von  Emperger;    in  the  absence  of  the  author  pre- 
sented by  the  Secretary. 
The  meeting  adjourned  until  Thursday  at  10.30  a.  m. 


Thursday,  March  14,  1912,  10.00  a.  m. 

Meeting  of  the  Section  on  Treatment  of  Concrete  Surfaces. 
President  Richard  L.  Humphrey  in  the  chair. 
The  meeting  took  the  form  of  a  topical  discussion  on  the 
coloring  of  concrete  surfaces,  contraction,  dusting  of  floors,  etc. 


Seventh  Session— Thursday,  March  14,  1912,  10.30  a.  m. 

President  Richard  L.  Humphrey  in  the  chair. 
The  following  papers  were  read  and  discussed: 

"Concrete  Highway  Bridges,"  by  William  Scott  Gearhart. 

"Concrete  Bridges,"  by  Daniel  B.  Luten. 

"Flat  Slab  Bridges,"  by  William  H.  Finley;  in  the  absence 
of  the  author  read  by  the  President, 
The  meeting  adjourned  until  8.00  p.  m, 


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Summary  of  Proceedings,  Eighth  Convention.         25 

Eighth  Session — ^Thursday,  March  14,  1912,  8.00  p.  m. 

President  Richard  L.  Humphrey  in  the  chair. 
The  paper  on  "The  Necessity  for  Good  Roads/'  by  Logan 
Waller  Page,  was  in  the  absence  of  the  author  presented  by  E.  L. 
Eldredge. 

The  following  papers  were  then  presented : 

"The  Necessity  of  National  Aid  in  Good  Roads,"  by  H.  C. 

Gilbert. 
"Cement  Paving  as  Constructed  at  Mason  City,  Iowa,"  by 

F.  P.  Wilson. 
"An  Improved  Concrete  Pavement,"  by  E.  W.  Groves. 
The  report  of  the  Committee  on  Roadways,  Sidewalks  and 
Floors,  was  presented  by  the  Chairman,  C.  W.  Boynton,  and 
the  following  action  taken: 

Proposed  revisions  of  the  Standard  Specifications  for  Con- 
crete Road  and  Street  Pavements  ordered  to  letter  ballot. 

The  proposed  revision  of  the  Specifications  on  Sidewalks, 
Curb  and  Gutter,  and  the  proposed  new  Specifications  for  Plaiin 
and  Reinforced  Concrete  Floors,  were  considered  and  referred 
to  the  Committee  for  report  at  a  later  session. 

The  meeting  then  adjourned  until  Friday  at  10.30  a.  m. 


Friday,  March  15,  1912,  9.00  a.  m. 

Meeting  of  the  Section  on  Roadways,  Sidewalks  and  Floors; 
C.  W.  Boynton,  Chairman  of  the  Section,  in  the  chair. 

The  meeting  took  the  form  of  a  discussion  on  concrete  roads, 
concrete  floors,  the  prevention  of  dusting  of  floors,  concreting  in 
freezing  weather,  etc. 


Ninth  Session— Friday,  March  15,  1912,  10.30  a.  m. 

President  Richard  L.  Humphrey  in  the  chair. 
The  following  papers  were  read  and  discussed: 

"Concrete  Fence  Posts,"  by  L.  J.  Hotchkiss. 

"The  Design  of  Reinforced  Concrete  Retaining  Walls,"  by 
John  M.  Meade. 


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26        Summary  of  Proceedings,  Eighth  Convention. 

"Advantages  and  Durability  of  Cement  Sewer  Pipe/'  by 
Gustave  Kaufman;    in  the  absence  of  the  author 
presented  by  the  President. 
"Methods  of  Testing  Cement  Pipe,"  by  Duff  A.  Abrams; 
in  the  absence  of  the  author  presented  by  W.  A.  Slater. 
"The  Manufacture  and  Use  of  Cement  Drain  Tile,"  by 
Charles  E.  Sims. 
The  report  of  the  Committee  on  Cement  Products  and  Build- 
ing Blocks  was  in  the  absence  of  the  Chairman,  Percy  S.  Hudson, 
presented  by  Clarence  K.  Arp.    On  motion  the  Proposed  Standard 
Recommended  Practice  for  Cement  Tile  was  referred  to  letter 
ballot. 

The  Committee  on  Roadways,  Sidewalks  and  Floors,  C.  W. 
Boynton,  Chainnan,  reported  back  the  matters  referred  to  it 
and  on  motion  the  following  were  referred  to  letter  ballot: 

Proposed    Revisions   of   the    Standard    Specification    for 

Portland  Cement  Sidewalks. 
Proposed   Revisions   of  the   Standard   Specifications   for 

Portland  Cement  Curb  and  Curb  and  Gutter. 
Proposed    Standard    Specifications    for    Plain    Concrete 

Floors. 
Proposed  Standard  Specifications  for  Reinforced  Concrete 
Floors. 
The  report  of  the  Committee  on  Nomenclature  was  in  the 
absence  of  the  Chairman,  Peter  Gillepsie,  presented  by  Frank  C. 
Wight  and  was  on  motion  accepted  as  information. 
The  Committee  on  Education  reported  progress. 
The  Convention  then  adjourned  until  Saturday  at  10.30  a.  m. 


Saturday,  March  16,  1912,  9.30  a.  m. 

Meeting  of  the  Section  on  Building  Blocks  and  Cement 
Products,  President  Richard  L.  Humphrey  in  the  chair. 

The  meeting  discussed  the  materials,  methods  of  manufacture 
and  tests  of  cement  drain  tile. 


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SuMMABY  OP  Proceedings^  Eighth  Convention.        27 

Tenth  Session — Saturday,  March  16,  1912,  10.30  a.  m. 

President  Bichard  L.  Humphrey  in  the  chair. 
The  paper  by  George  Gibbs  on  "Some  Notes  on  the  Value 
and  Comparative  Cost  of  Reinforced  Concrete  Telegraph  Poles," 
was  in  the  absence  of  the  author  presented  by  the  President. 

The  President  read  in  the  absence  of  the  author,  Robert  A. 
Cummings,  the  paper  on  "The  Making  and  Driving  of  Rein- 
forced Concrete  Piles  Within  Six  Days." 

The  paper  by  W.  J.  Towne  on  "Concrete  Fence  Posts," 
was  in  the  absence  of  the  author  read  by  title. 

A  paper  on  "Comparative  Tests  of  the  Strength  of  Concrete 
in  the  Laboratory  and  in  the  Field,"  was  presented  by  R.  J.  Wig. 
The  following  papers  were,  in  the  absence  of  the  authors, 
read  by  title: 

"Field  Inspection  and  Tests  of  Materials  for  Reinforced 

Concrete,"  by  G.  H.  Bayles. 
"Unit  Cost  of  Reinforced  Concrete  for  Industrial  Build- 
ings," by  C.  S.  AUen. 
"Notes  on  "the  Deformation  in  the  Webs  of  Rectangular 
Concrete  Beams,"  by  H.  C.  Berry. 
The  President  then  presented  a  paper  by  Alfred  D.  Flinn 
on  "The  Use  of  Cement  for  Protecting  Steel  Pipes  Along  the 
New  York  Aqueduct." 

Robert  F.  HavUk  presented  a  paper  on  "Modem  Methods  of 
Manufacturing  Concrete  Products,"  which  was  followed  by  a 
discussion. 

The  meeting  then  adjourned  until  8.00  p.  m. 


Eleventh  Session — Saturday,  March  16,  1912,  8.00  p.  m. 

President  Richard  L.  Humphrey  in  the  chair. 

The  paper  on  "The  Use  of  Concrete  in  the  Fourth  Avenue 
Subway,  Brooklyn,  N.  Y.,"  was  in  the  absence  of  the  author, 
Frederick  C.  Noble,  presented  by  the  President. 

W.  A.  CoUings  presented  a  paper  on  "Reinforced  Concrete 
in  Agriculture." 


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28         Summary  of  Proceedings,  Eighth  Convention. 

The  paper  by  S.  B.  Williamson  on  "The  Handling  of  Concrete 
in  the  Construction  of  the  Panama  Canal,"  was  in  the  absence  of 
the  author,  presented  by  the  President. 

The  following  papers  were  then  read  and  discussed: 

"The  Present  Status  of  Iron  Portland  Cements,"  by  P.  H. 

Bates. 
"Iron  Portland  Cement,"  by  Herman  E.  Brown;    in  the 
absence  of  the  author,  presented  by  the  President. 
The  Committee  on  Resolutions,  Rudolph  P.  Miller,  Chair- 
man, presented  the  following  resolutions,  which  were  unanimously 
adopted: 

(a)  Resolved  J  That  a  eommittoo  bo  appoint  od  by  the  Executive  Board 
to  consider  the  form  of  all  standard  specifications  or  recommende<i  practice 
issued  by  this  Association  with  a  view  to  securing  uniformity  so  far  as  prac- 
ticable. 

(6)  Resolved,  That  a  committee  of  five  members  of  this  Association,  of 
which  one  member  shall  be  Chairman  of  the  Committee  on  Specifications 
and  Methods  of  Tests  for  Concrete  Materials,  be  appointed  by  the  President 
to  plan  a  comprehensive  and  systematic  investigation  of  the  aggregates  used 
for  concrete  and  to  interest  State  Universities,  Experiment  Stations  and 
other  laboratories  in  carrying  out  the  same. 

(c)  Resolved,  That  the  Executive  Board  be  instructed  to  consider  the 
advisability  of  appointing  a  Committee  to  report  on  Standard  Specifications 
for  Concrete  Highway  Bridges  and  (Culverts. 

(d)  Resolved,  That  the  Committee  on  Nomenclature  be  instructed  and 
empowered  to  extend  its  work  to  include  the  standardization  of  the  size  of 
drawings,  the  symbols  used  on  same  and  the  graphical  representation  of 
details. 

Resolved,  That  the  Committee  on  Cement  Products  be  instructed  to 
consider  the  suggestions  and  criticisms  on  building  block  specifications  offered 
at  this  Convention,  to  confer  with  the  Committee  on  Reinforced  Concrete 
and  Building  Laws  with  a  view  to  reconciling  there  commendations  of 
the  two  committees,  and  to  report  revised  specifications  to  the  next 
convention. 

(c)  Resolved,  That  a  report  be  submitted  to  the  next  Convention  on 
Standard  Specifications  for  Concrete  Fence  Posts  and  that  the  Executive 
Board  consider  the  advisability  of  having  this  done  by  a  sub-committee  of 
the  Committee  on  Cement  Products  or  by  a  separate  committee. 

(/)  Resolved,  That  the  thanks  of  this  Association  are  hereby  tendered 
the  officials  and  the  representatives  of  the  local  engineering  and  concrete 
interests  for  their  hearty  welcome,  to  the  citizens  of  Kansas  City  for  their 
co-operation  in  making  this,  the  Annual  Convention,  a  notable  success,  and 
to  the  guests  of  the  Association  for  their  assistance  in  this  success  by  the 
contribution  of  their  interesting  and  valuable  papers. 


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Summary  of  Proceedings,  Eighth  CoNVENTioN.         2§ 

(g)  Reaolvedf  That  the  thanks  of  this  Association  are  hereby  tendered 
to  the  members  who  have  aided  by  the  presentation  of  papers,  to  the  several 
committees  whose  efforts  have  added  this  meeting  to  the  long  series  of  suc- 
cessful conventions,  to  the  local  and  technical  press  whose  recognition  of 
the  work  of  this  organization  is  gratefully  acknowledged,  and  to  its  officers 
but  particularly  to  its  President,  Mr.  Richard  L.  Humphrey,  for  his  untiring 
devotion  to  the  interest  and  welfare  of  this  Association. 

The  President  thereupon  declared  the  meeting  adjourned, 
sine  die. 


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National  Association  of  Cement  Users. 


PROCEEDINGS 

OF  THE 

EIGHTH    CONVENTION 


This  ABSOciation  is  not  responsible,   as   a  body,  for  the  statements  and 
opinions  advanced  in  its  publications. 


EUROPEAN   PRACTICE   IN    CONCRETE    CON- 
STRUCTION. 

Annual  Address  by  the  President, 
Richard  L.  Humphrey.* 

Two  years  ago,  in  speaking  on  the  use  of  concrete  in  Europe, 
I  discussed  in  a  general  way  the  progress  that  was  being  made 
and  contrasted  the  conditions  prevailing  in  various  parts  of 
Europe.  It  was  also  pointed  out  that  in  the  artistic  treatment 
of  concrete  the  foreign  engineer  and  architect  undoubtedly  showed 
greater  skill  than  was  shown  in  this  country,  and  therefore  obtained 
much  more  pleasing  results.  I  further  commented  on  the  fact 
that  the  development  of  the  use  of  concrete  in  certain  countries 
was  very  much  handicapped  by  restrictive  building  laws.  It  was 
my  good  fortune  to  again  visit  Europe  last  year  and  to  inspect 
extensively  various  structures  of  concrete,  covering  the  most 
important  work  west  of  the  Russian  boundary.  I  shall  use  this 
opportunity  for  enlarging  upon  my  former  address,  pointing  out  the 
development  and  essential  points  of  difference  at  the  present  time 
in  reinforced  concrete  construction  in  this  country  and  in  Europe. 

This  visit  to  Europe  and  the  inspection  of  concrete  construc- 
tion during  the  closing  months  of  last  year,  was  under  more  favor- 
able conditions  than  on  the  occasion  of  my  previous  trip,  in  that 
I  was  a  guest  generally  of  the  concrete  associations,  whose  officers 
did  all  in  their  power  to  show  me  everything  of  interest.  This 
was  particularly  true  of  my  visit  to  Austria,  where,  as  the  Presi- 


*  Consulting  Engineer,  Philadelphia,  Pa. 

(31) 


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S^  Annual  Address  by  the  President. 

dent  of  this  and  Honorary  Member  of  the  Austrian  Concrete 
Association,  I  was  the  guest  of  the  latter  during  my  entire  stay 
in  that  country,  and  was  under  the  devoted  personal  guidance 
of  its  Director,  Karl  Bitner.  This  gentleman,  as  you  know,  was 
a  delegate  to  our  New  York  Convention  and  one  of  the  speakers 
at  the  banquet,  and  I  wish  again  to  express  my  heartiest  thanks 
and  appreciation  for  the  courtesies  ext^^nded  to  me  and  the 
unusual  efforts  which  he  made  to  render  my  visit  a  pleasant  and 
profitable  one.  It  is  certainly  true  that  this  opportunity  of 
inspecting  the  concrete  buildings  in  Austria  was  a  valuable  one 
for  the  reason  that  some  of  the  best  examples  of  concn^te  con- 
struction are  to  be  found  in  that  country. 

The  Austrian  Concrete  Association  has  always  manifested 
a  great  interest  in  the  work  of  our  Institute  and  showed  a  willing- 
ness to  co-operate  with  us  in  every  possible  way.  The  unusual 
character  of  the  program  laid  out  and  the  rapidity  with  which 
various  pieces  of  work  were  inspected  was,  I  think,  intended  as 
a  tribute  to  our  American  characteristics.  I  submit  this  inter- 
esting program.     (See  opposite  page.) 

A  feature  that  impressed  me  most  favorably  was  that  my 
visits  to  the  various  buildings  had  been  arranged  for  in  advance 
and  upon  scheduled  time.  On  our  arrival  at  the  building  we 
were  met  by  the  architect  or  his  representative,  the  builder,  and 
the  engineer  in  charge;  in  many  instances  the  plans  of  the  struc- 
ture were  tacked  up  at  some  convenient  point,  and  before  the 
building  was  inspected  a  representative  who  spoke  English  ex- 
plained the  particular  points  of  interest  in  the  structure.  On 
Thursday  night  I  was  the  guest  of  the  Austrian  ('oncrete  Institute, 
the  Austrian  Association  of  Cement  Manufacturers,  Austrian 
Society  of  Engineers  and  Architects  and  the  Austrian  Clay  Products 
Association.  My  here  recorded  acknowledgment  of  the  signal 
honor  conferred  upon  me  but  inadequately  expresses  th(»  (l(»pth 
of  my  gratitude  and  the  extent  of  my  appreciation.  The  precis- 
ion with  which  the  progran  was  carried  out,  the  completeness  of 
the  details  and  the  warm  hospitality  extended  to  me  by  all  those 
I  met,  has  left  its  permanent  record — one  that  I  shall  never  forget. 

Dm-ing  my  visit  to  p]ngland  it  wius  my  privilege  to  address 
the  Concrete  Institute  in  London,  on  October  26,  1911,  on  the 
subject  of  "  Fireproofing**  for  which  I  was  honored  by  the  award 
of  the  Institute  medal. 


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OSTERREICHISCHER  BETONVEREIN 
WIEN,   IV/2,   MOLLWALDPLATZ  4 

TELEPHONE   NT.    10.597  TELEPHONE    Nr.    10.597 


ZEITEINTEILUNG 

anlasslich 

Des  Besuches  des  Prasidenten  der  National  Association  of  Cement 

Users,  Herrn  RICHARD  L.  HUMPHREY,  Consulting  Engineer, 

Philadelphia. 


Donnerstag,  21.  September,  1911. 

9  Uhr  30  Min.     Abfahrt  vom  Hotel  Bristol: 

9     "     35      "        Kamtnerhofbasar,  I.  Kamtnerstrasse 

(Ed.  Ast  ACic); 

10     "     20      "        Wohn-  iind  Geschaftshaus,  I.  Weihburggasse  7 
(Plachy  &  Co.); 

10     "     30      "        Wohn  -und  Geschaftahaus,  I.  Weihburggasse  9 
(G.  A.  Wayss&  Cie.); 

10     "     40      "        Wohn-  und  Geschaftshaus,  I.  Weihburggasse  10 

(N.  Rella  &  Xcffe) : 

10  "     50       *        Lazzenhof,  I.  Rotenturmstrasse,  verlangeter  Fleischmarkt 

(Kontrollbalkenversuch) 
(k.  k.  Oberbaurat  Dr.   Ing.   Friti  von  Empergcr  —  Chefingenieur 
Richard  Wucakowski) 

11  "     30     *'        Wiener  Urania,  I.  Aspernplatz 

(G.  A.  Wayss&Cie.): 

11  "     55      *'        Dreilaufferhaus,  I.  Kohlmarkt,  Ecke  Herrengasse 

(Pittel  &  Brausewettrr) ; 

12  "     00      "         Wiener  Bankverein,  I.  Schottenring 

(Ed.  Ast  A  Cie.  und  N.  Rella  &  Neflfe); 

12     "     30      "        Lunch  im  Rathauskeller: 


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2  Uhr  00  Min.      Autogarage,  II.  Rembrandtstrasse  29 

(Jancsch  und  Schnell) ; 

40  "  Basaltoidpflaster  (2  Jahre  alt),  XVI.  Hasnerstrasee— 
Richard  Wagner-Platz 

(Baaaltwprke  Radebeulo) ; 
55      "        Kirchenbau,  XVI.  Herbststrasse  66 

(MazEtnerA  Cie.); 

25  "  Zentralpalast,  VI.  Mariahilferstrafise  —  Ecke  Kaiser- 
strafTe 

(G.  A.  Waysa  &  Cie.) ; 

00      ''        Gewerbliche  Fortbildungsschule,  VI.  Mollardgasse 

(N.  Rella  ANeffe): 

20  "  Schokoladefabrik  Stollwerck,  V.  Gaudenzdorfer  GOrtel 
43,45 

(Pittol  A  Braiwewett^r) ; 

30      "        Schule,  V.  Margaretenstrasse  103 

(N.  RellaANeffe); 

15      "        Kronenbrotwerke,  X.  Siccardsburggasse  83 

(Ed.  Ast  A  Cie.) ; 

Wahrend  der  Fahrt  zu  besichtigen: 
Kabelblocklegung  ftir  die  Telephonleitungen,  Unterleitung 
der    Strafisenbahn,    Stadtbahn    als    Untergnind-    und 
Hochbahn  etc. ; 

00       **       Besuch  des  k.  k.  Hof-Opemtheaters; 
Souper. 

Freitag,  22.  September. 

Fahrt  nach  Berndorf,  Besichtigung  der  Kirche,  Weiterfahrt 
nach  Weissenbach,  Besichtigung  der  Kunststeinfabrik; 
Adolf  Baron  Pittel 

Lunch; 

Weiterfahrt; 

Besichtigung  der  Zementfabrik  Achau; 

Besichtigung  der  Betriebsanlagen  der  Wienerberger 
Ziegelfabriks^  und  Baugesellschaft  (Keramitfabrik  und 
Seidlbalkenerzeugung),  X.  Triesterstrasse  100; 

00  "  Souper  am  Cobenzl,  angeboten  vom  Osterreichischen 
Betonverein,  Verein  Osteneichischer  Zementfabrik  an- 
ten,  Osterreichischen  Ingenieur-  und  Architektenverein 
und  Osterreichischen  Tonindustrievcrein  (bei  schlechtem 
Wetter  Souper  im  Ktlnstlerzimmer  des  Restauj^ants 
Hopfner). 


8  Uhr  00  Min 

11 

u 

30 

t 

1 

It 

45 

ft 

3 

tl 

00 

tt 

4 

tt 

30 

tt 

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«9 

"     16 

9 

"     30 

9 

"     45 

10 

"     05 

Samstaflp  23.  September. 

8  Uhr  00  Min.     Abfahrt  vom  Hotel  Bristol: 

8  ''  30  "  Versuchsplatz  des  Eisenbetonausschusses  des  OsteireichiB- 
chen  Ingenieur-  und  ArchitektenvereineSi  Wien,  XIX. 
Muthgasse; 

SchleuBenanlagen  in  Nussdorf ; 

Waaserturm  am  Bahnhof  HeiUgenstadt 
(N.  Rella  A  Neffe): 

Zigarettenpapierfabrik  Schnabl,  XIX.  HeiUgenstadt 

(N.  Rella  &  Neffe); 

Brtlcke  im  Zuge  der  Rampengasse,  XIX. 
fH.  RelUftCo.); 

10     "     20      **        Wagenhalle    der    stjidtbchen    Strassenbahnen,    XVIII. 
Wahringer  Gtirtel 
(N.  Rella  ft  Neffe); 

10  "     45      "        Physikalisches  Institut,  IX.  Wahringerstrasse  —  Waisen- 

hausgasse 
(Ed.  .\pt<fcCie.); 

11  "     30      "        Sargfabrik,  XIII.  Matznergasse  8 

(A.  Porr): 

11  "     50      "        Technisches  Museum  ftir  Industrie  und  Gewerbe,  XIV. 

Ecke  Winckelmannstrasse  und  Linzerstrasse 

(A.  Porr); 

12  ''     30      ''        Basaltoidflaster,  XIII.  Sch5nbrunner  Schloesstrasse 

(Basaltwerke  Radebeule); 

Lunch  im  Parkhotel  (Hietzing); 

Landes-Heil-  und  Pflegeanstalt  Steinhof ; 

Kohlenturm    und    Koksseperationsanlage    im    Gaswerke 
XXI.  Leopoldau 
(H.  Rella  A  Co.): 

4  "  30  "  Siloanlage  nebst  Weichraum  und  Lagerraum  in  der 
Malzfabrik  Hauser  &  Sobotka,  XXI.  Stadlau 

(H.  Rella  A  Co.); 

Sehenswtkrdigkeiten  von  Wien; 
8     "     00      "        Souper  Venedig  in  Wien. 

Eventuell:  Sonntag,  24.  September. 

Unter  Ftlhrung  des  Herm  Ingenieur  E.  A.  Westermann, 
Chef  der  Firma  Wayss,  Westermann  &  Cie.,  Graz: 

Fahrt  tiber  den  Semmering  nach  Graz,  Besichtigung  des 
Landeskrankenhauses  Graz  und  der  Briickenobjekte  an 
der  Bahnstrecke  Weiz-Birkfeld. 


12 

"     46 

2 

"     15 

3 

"     30 

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Montag,  28.    Sentember. 

Fahrt  nach  Retznei,  Besichtigung  der  Zexnentfabrik, 
Weiterfahrt  nach  Adelsberg,  Besichtigung  der  Adels- 
berger  Grotte; 

Fahrt  nach  Triest,  Besichtigung  der  Hangarbauten, 
Fundierungen  etc. 


Dienstag,  26.     September. 


8  Uhr  00  Min.      Excelsior  Palace  Hotel 

(Wayas'  Wefltcrmann  &  Cie.) ; 

8     "     30      "        Greinitz 

(Maxorana  A  Cornel) ; 

8  "    45      "        Riunione  Adriatica 

(Aat.  ACie.): 

9  '*     00      "        Hanger  -Bauten 

(WayM*  Freitag  &  Mciaong); 

10-12  ''  Rundfahrt  im  Hafen; 

Eventuell:  Souper  in  Opcina; 

Fahrt  nach  Miramare. 


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Annual  Address  by  the  President. 


33 


The  various  countries  of  Europe  are  progressing  in  the  use 
of  concrete,  but  many  of  the  large  cities  are  still  handicapped  by- 
restrictive  building  laws;  particularly  is  this  true  of  London, 
where  only  recently  have  the  London  County  Council  Regula- 
tions permitted  the  erection  of  structures  that  might  be  termed 
reinforced  concrete.  Most  continental  countries  show  far  greater 
skill  in  the  application  of  concrete  than  is  shown  in  England, 
where  the  British  conservatism  has  resulted  in  heavy  structures 
of  very  simple  application.  This  is  also  true  for  the  most  part 
of  the  various  cities  in  Germany.  In  France,  in  Belgiimi,  and 
particularly  in  Austria  a  wider  and  less  conservative  grasp  in  the 
use  of  this  material  has  resulted  in  the  erection  of  structures 


'AHDi   JIMMf^H'^C 


i4*'/l'*"l#  KMVffil'J 


FrKFf'dQOFING, 


FIG.   1. — THE  CONCRETE  INSTITUTE  MEDAL. 

which  are  not  equaled  anywhere  in  the  world.  Certainly  at  the 
present  time  in  Vienna  I  believe  one  may  find  the  most  extensive 
use  of  concrete  that  is  to  be  found  either  in  this  country  or  Europe. 
The  city  of  Hamburg  is  perhaps  second  only  to  Vienna  in  the 
number  of  its  reinforced  concrete  buildings,  and  these  two  cities 
are  the  most  progressive  spots  in  Europe.  I  observed  on  this 
trip  that  more  concrete  buildings  were  in  evidence  in  the  out- 
skirts of  London  and  other  English  and  continental  cities  than  on 
my  previous  visit;  in  this  country  the  same  is  true,  probably 
for  the  same  reason,  viz.,  that  the  laws  governing  the  erection  of 
buildings  are  more  liberal  outside  of  than  inside  of  the  larger  cities. 
The  development  of  the  use  of  concrete  is  certainly  much 
greater  in  Europe  than  it  was  two  years  ago.  I  do  not  think, 
however,  that  Europe  as  a  whole  shows  as  great  a  development 


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34  Annual  Address  by  the  t^REsiDEKf. 

as  is  to  be  found  in  this  count^>^  In  certain  parts  of  Europe, 
Austria,  for  example,  is  shown  a  greater  knowledge  and  skill  in 
the  use  of  this  material.  In  England,  especially  in  London, 
where  there  were  practically  no  concrete  buildings  to  be  foimd  on 
my  visit  two  years  ago,  there  are  now  to  be  found  many  struc- 
tures of  reinforced  concrete;  although  it  is  true  that  these  are 
not  within  the  limits  of  the  authority  of  the  London  County 
Council,  which  permits  only  reinforced  concrete  for  floors  with 
masonry-bearing  walls,  and  to  a  limited  extent  for  columns.  It  is 
probable,  since  a  recent  revision  of  the  London  County  Building 
regulations  permits  the  use  of  reinforced  concrete,  that  from 
now  on  many  structiu'es  wall  be  erected  of  reinforced  concrete. 

The  materials  in  Europe  available  for  use  in  concrete  are 
still  relatively  more  expensive  than  labor.  As  a  result,  the 
designer,  for  purposes  of  economy,  finds  it  desirable  to  so  shape 
his  forms  as  to  eliminate  as  much  as  possible  all  material  which 
is  not  required  for  structural  or  protective  purposes.  The  effect 
of  this  is  to  render  the  structure  less  massive  and  more  pleasing 
in  appearance.  The  abundance  of  extremely  cheap  unskilled 
labor  and  the  presence  of  low-priced  technically-trained  labor  is 
one  of  the  great  advantages  in  the  erection  of  concrete  struc- 
tures in  Europe.  This  is  particularly  true  as  to  the  foremen 
and  labor  bosses  who,  in  many  cases,  especially  in  Germany,  are 
technically-trained  men,  which  is  of  course  unusual  in  this  country. 

Another  feature  which  tends  to  increased  efficiency  in  the 
erection  of  concrete  structures  is  the  fact  that  there  are  govern- 
mental regulations  which  apply  with  sufficient  rigidity  to  terri- 
tory outside  of  the  large  cities.  In  large  cities  the  regulations  are 
necessarily  much  more  rigid.  There  is  a  wholesome  respect  for 
the  law  throughout  Europe — ^which  is  lacking  in  this  country — 
with  the  result  that  each  person  concerned  conscientiously  en- 
deavors to  erect  the  structure  in  full  accordance  with  the  building 
regulations.  In  some  countries,  especially  Germany,  a  contractor 
who  is  found  guilty  of  dishonest  practices  loses  caste  and  becomes 
discredited,  which  is,  after  all,  the  most  effective  way  of  pre- 
venting the  construction  of  dishonest  structures.  I  recall  par- 
ticularly a  case  in  Stuttgart  where  what  might  properly  be  called 
a  "Quantity"  engineer,  having  assumed  responsibility  for  the 
erection  of  the  building,  was  arrested  and  sentenced  to  several 
years  imprisonment  by  reason  of  the  collapse  of  the  structure  of 


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Annual  Address  by  the  President.  35 

which  he  had  assumed  the  responsibility.  Another  effective  way 
of  dealing  with  this  subject  is  practiced  in  France,  especially  in 
Paris,  where  the  building  department  acts  merely  as  a  custodian 
of  plans;  the  law  placing  the  responsibility  for  the  structure  on 
the  architect,  contractor  and  owner.  Under  the  law,  these  three 
parties  are  held  to  be  responsible  for  the  collapse  of  the  structure 
until  their  innocence  is  established.  The  use  of  cheap  labor, 
especially  women,  to  carry  mortar  and  concrete  in  small  tubs  on 
the  head,  seems  to  be  the  usual  method  but  hardly  an  effective 
one  for  handling  concrete.  In  the  erection  of  but  two  buildings 
did  I  see  used  the  elevating  machine,  so  commonly  used  in  this 
country,  for  handling  concrete. 

The  presence  of  a  large  number  of  women  laborers  on  con- 
crete structures  was  always  a  source  of  interest  to  me  as  was 
also  the  pittance  that  these  women  were  paid  for  a  day's  work. 
A  recent  lecturer  in  New  York  stated  that  in  African  hunting 
expeditions  the  camp  followers  received  about  sixty  cents  a  month. 
While  these  women  do  not  receive  so  little,  yet  when  you  con- 
sider that  in  the  one  case  the  men  were  furnished  their  food, 
while  in  the  other,  the  women  had  to  supply  it  themselves,  the 
wage  paid  the  women  (in  some  countries  equal  to  16  cents  and  as 
low  as  12J  cents  a  day)  is  extraordinarily  low  and  you  can  appre- 
ciate why  elevating  and  conveying  machinery  is  doubtless  more 
expensive  than  labor.  The  almost  imiversal  limit  of  about  5 
stories  or  22  metres  in  the  height  of  all  structures  renders  ele- 
vating and  conveying  machinery  relatively  unimportant.  When, 
however,  speed  in  the  erection  of  concrete  structures  becomes 
important,  Europe  will  be  obliged  to  resort  to  mechanical  means 
for  elevating  and  conveying  concrete,  as  the  method  of  carrying 
concrete  in  tubs  on  the  heads  of  the  laborers  is  too  slow  for  proper 
continuous  placing. 

Fig.  2  is  a  view  of  the  memorial  church  at  Berndorf,  the 
industrial  village  of  the  Krupp  works,  just  outside  of  Vienna, 
in  which  will  be  seen  a  nimiber  of  the  women  laborers  who  are 
engaged  in  carrying  mortar  and  concrete  in  the  manner  above 
described.  These  women,  in  spite  of  their  skirts,  are  able  to  climb 
ladders  with  almost  the  same  speed  as  men. 

The  use  of  round  timbers  instead  of  sawed,  as  studs  for  forms 
and  scaffolding,  is  quite  general.  Where  a  splice  is  necessar>'^, 
the  two  parts  are  tied  together  with  rope  or  chain.     They  do 


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38 


AN^UAL^ApbRESS  Bt  I'&E   t^RESlfiENT^. 


not  use  nails,  therefore,  these  timbers  can  be  used  over  and  over 
again  and  last  for  such  a  length  of  time  as  to  make  the  cost  rela- 
tively very  low.  Another  interesting  construction  detail  is  the 
method  of  splicing  uprights  through  the  medium  of  two  iron 
rectangular  iron  bands  siurounding  the  uprights,  which  are  clamped 
tightly  together  by  wedges  between  the  inside  of  the  band  and  the 
face  of  one  of  the  uprights,  which  is  a  very  simple  and  readily 
adjustable  device.  This  particular  device  was  used  on  the  props 
in  the  construction  of  the  Commercial  Museum  in  Vienna. 

The  development  in  the  use  of  reinforced  concrete  telephone 


na.   2. — DOME   MEMORIAL   CHURCH  IN  BERNDORF,   AUSTRIA. 

and  telegraph  poles  is  even  greater  than  it  was  on  my  previous 
visit  and  the  experience  gained  has  brought  forth  many  orna- 
mental and  efficient  poles;  the  tendency  for  purposes  of  economy 
is  towards  a  hollow  pole,  this  being  of  greater  necessity  in  Europe 
than  in  America;  and  in  my  judgment  the  cost  of  the  concrete 
pole  must  be  materially  reduced,  to  effectually  compete  with  the 
wooden  pole  in  this  country.  The  view  shown  (Fig.  3)  of  the 
centrifically  molded  circular  poles  in  Bad  Kosen  indicates  the 
uniformity  and  symmetrical  shape  of  this  pole.  This  circular 
form,  however,  is  not  necessary,  and  there  are  many  hollow  poles 
of  ornamental  character  of  square  or  octagonal  design,  notably 


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Annual  Address  by  the  President. 


37 


four  in  Dresden,  in  the  Exposition  of  Hygiene.  The  ornamental 
poles  on  the  Augusta  Bridge  in  Dresden  further  exemplify  the 
beauty  of  this  type  of  pole,  the  hollow  interior  affording  an  ideal 
place  for  running  the  electrical  wires. 

The  method  on  making  the  hollow  reinforced  concrete  pole 


FIG.  3. CENTRIFUGALLY    MOLDED    CIRCULAR    TOWN    ELECTRIC    LIGHT    POLES, 

IN   BAD   KOSEN,    GERMANY. 

consists  in  placing  the  mold  filled  with  concrete  in  a  machine 
rotated  at  the  rate  of  600  revolutions  per  minute.     The  effect  of* 
this  high  speed  is  to  force  the  concrete  against  the  walls  of  the 
mold  by  centrificial  action,  gradually  compacting  the  concrete 
and  forming  a  hollow  space  in  the  center  of  the  pole  in  which 


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38  Annual  Address  by  the  President. 

the  excess  water  and  laitance  gathers  producing  an  exterior  sur- 
face of  a  hard  and  uniform  texture  which  greatly  adds  to  the 
appearance  of  the  pole.  The  molds  are  generally  kept  on  the 
pole  until  properly  hardened. 

The  poles  erected  in  connection  with  the  Danish  railways  in 
Copenhagen,  Denmark,  are  hollow,  36  ft.  high,  and  were  molded 
by  the  hand  process  and  the  tests  showed  them  to  be  very  stiff  and 
capable  of  resisting  high  loads. 

It  has  been  found  in  Europe,  especially  where  lumber  is 
becoming  scarce,  that  reinforced  concrete  poles  are  much  more 
efficient  and  less  costly  than  wooden  poles;  that  the  maintenance 
of  the  line  is  less  expensive  and  the  permanent  life  of  the  pole 
much  greater.  It  appears  to  me  to  be  evident  that  in  order  to 
effect  the  desired  economy  in  the  cost  of  manufacture  of  this 
class  of  concrete  products,  it  is  necessary  to  turn  out  a  great 
many  each  day;  inasmuch  as  they  are  coming  into  general  use 
in  Europe,  there  is  a  constant  decrease  in  the  cost  of  manufacture. 

The  poles  illustrated  in  Fig.  4  are  those  at  the  plant  of  R. 
Wolle  in  Leipsic,  Germany.  There  seems  to  be  a  general  use  for 
concrete  poles  for  carrying  high-tension  lines,  especially  where 
the  pole  must  be  of  considerable  height.  It  is  claimed  that  the 
cost  of  maintenance  of  such  lines  is  very  much  less  than  for 
wooden  poles.     This  probably  accounts  for  their  popularity. 

The  continued  use  of  reinforced  concrete  poles  in  this  country 
leads  to  the  belief  that  as  the  number  of  poles  and  skill  in  making 
them  increases  they  will  become  more  serious  competitors  of  the 
wooden  pole  and  will  in  time  replace  the  other  forms  of  telephone, 
telegraph  and  electric  transmission  poles.  They  can  be  molded 
to  suit  the  particular  conditions  of  almost  any  height  and  can  be 
so  anchored  in  the  ground  as  to  enable  them  to  maintain  a  rigid 
position  in  almost  all  soils.  The  high  tension  transmission  line 
poles  of  reinforced  concrete,  used  in  connection  with  the  Penn- 
sylvania Railroad  tunnels,*  which  were  erected  on  a  mattress  in 
the  marshy  land  of  the  approaches  on  the  New  Jersey  side,  are  an 
illustration  of  the  superior  excellence  of  this  type  of  pole. 

Another  matter  which  was  of  considerable  interest  to  me 
was  the  form  of  chimney  developed  by  Captain  F.  Mohl  in  Copen- 
hagen.    This  consists  of  a  four-leaf-clover  section  at  the  base 

♦See  rroc,  N.A.C.U.,  Vol.  VIII,  p.  769, 


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which  gradually  merges  mto  a  circular  at  the  top.  A  num- 
ber of  these  chimneys  have  been  erected,  some  of  considerable 
height,  and  it  is  said  that  they  are  more  economical  and  much 
more  suitable  than  the  ordinary  circular  stack. 

The  reinforced  concrete  barges  shown  in  the  illustration  were 
photographed  (Fig.  5)  at  the  place  of  manufacture  in  Livomo, 
Italy.  These  particular  barges  were  used  for  handling  coal  and 
seemed  to  be  in  every  way  thoroughly  satisfactory.  When  the 
Italian  government  first  used  reinforced  concrete  for  armor  plate, 


FIG.   4. — TYPES    OF    REINFORCED     CONCRETE     POLES    AT    PLANT    OF    R.    WOLLE, 

LEIPSIC,  GERMANY. 

there  was  much  amusement  manifested  in  this  country  and  the 
average  person  believed  that  the  weight  of  this  material  would 
sink  the  boat.  Its  use,  therefore,  to  form  the  entire  hull  of  a 
boat  would  seem  even  more  quixotic.  Barges  and  other  vessels, 
especially  battleships,  are  made  entirely  of  steel,  which  is  heavier 
than  concrete;  and  when  you  consider  that  the  floating  of  the 
vessel  is  a  question  of  buoyancy  depending  on  the  lightness  of 
the  material  and  character  of  the  air-tight  compartments,  it  is 
evident,  I  think,  that  any  material  properly  designed  will  b^ 


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Annual  Address  by  the  President. 


suflSciently  buoyant  for  practical  purposes.  In  the  case  of  the 
armament  of  concrete,  which  is  much  lighter  than  steel,  the  thick- 
ness can  be  much  greater  and  the  toughness  of  the  former  material 
renders  it  a  better  protection.  I  believe  with  the  development 
of  the  art  of  reinforced  concrete  boat  construction,  these  vessels 
will  in  the  future  come  into  general  use  and  will  prove  most  ser- 
viceable and  economical,  both  as  to  first  cost,  maintenance  and 
durability. 

It  is  not  so  very  many  years  ago  that  the  concrete  barge  was 
a  novelty  and  regarded  by  many  as  a  freak  application  of  cement. 
However,  a  few  years'  trial  of  these  boats  has  resulted  in  striking 
economy  and  in  many  places  I  found  concrete  barges  being  used. 


FIG.   5. — REINFORCED   CONCRETE   BARGE   FACTORY   AT  LIVORNO,   ITALY. 

especially  of  the  canal  boat  type,  for  handling  coal  and  other 
materials.  It  has  been  found  that  the  durability  and  serviceability 
of  these  boats  render  their  ultimate  cost  very  much  less  than 
boats  made  of  any  other  material.  There  have  been  a  number 
of  such  boats  used  in  this  country,  notably  in  connection  with 
the  construction  of  the  Panama  Canal,  and  in  my  judgment 
there  will  be  an  even  greater  use  of  them  in  the  future. 

The  constant  study  of  the  reinforced  concrete  railroad  tie 
(with  somewhat  disappointing  results  at  the  present  time)  shows 
a  desire  for  a  tie  of  this  type.  In  parts  of  Europe  where  steel  or 
wooden  ties  are  readily  obtained  at  reasonable  cost,  the  concrete 
tie  does  not  make  much  headway.     In  other  parts  where  ties  of 


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timber  and  steel  are  expensive,  for  instance  in  Italy,  where  the 
steel  and  wood  tie  is  at  least  as  expensive  as  the  concrete,  there 
has  been  considerable  development  and  the  officials  informed  me 
that  more  than  300,000  were  in  use  in  the  Italian  railways  and 
that  there  were  contracts  for  upwards  of  a  million.  The  tie, 
however,  has  not  a  very  great  life  when  used  in  main  line  ser- 
vice, where  it  is  subjected  to  the  frequent  passage  of  heavy  loco- 
motives.    In  what  are  termed  secondary  lines  and  sidings,  ties 


FIG.   6. — ^REINFORCED    CONCRETE    TIES    IN    MAIN    LINE    ITALIAN    RAILWAY    AT 
PORTO   NACCIO,   ITALY. 

of  reinforced  concrete  are  reasonably  effective  and  in  Italy  have 
as  much  as  six  or  seven  years  of  life. 

I  inspected  some  railroad  ties  just  outside  of  Rome  and 
foimd  that  these  ties  (see  Fig.  6),  which  had  been  in  service  for 
about  two  years,  were  not  wearing  very  well.  A  number  of  ties 
having  crushed  just  inside  the  rail. 

The  method  of  fastening  the  tie  consists  of  the  use  of  a 
wooden  block,  cylindrical  in  shape,  which  is  driven  into  the  hole 
molded  in  the  tie  and  au  ordinary  wood  screw  which  fastens 


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Annual  Address  by  the  President. 


the  rail  to  the  tie.     When  the  threads  in  the  block  are  worn  by 
use,  the  block  is  replaced. 

Fig.  7  is  an  illustration  of  the  section  of  track  of  the  London 
and  Southeastern  Railway  at  Knockholt  station  in  which  rein- 
forced concrete  ties  have  been  used.  These  ties,  I  think,  are  not 
of  as  good  design  as  those  used  in  the  Italian  railways.  They 
have  been  in  service  about  two  years.  A  number  of  them  have 
failed  in  the  manner  shown  in  the  illustration  (Fig.  8)  by  the 
concrete  crushing  just  inside  the  rail.  It  is  my  opinion  that  the 
difficulty  in  reinforced  concrete  ties  is  in  a  lack  of  proper  analysis 


FIG.  7. — REINFORCED  CONCRETE  TIES  IN  SECTION  OF  LONDON  AND  SOUTHEASTERN 
RAILWAY   AT   KNOCKHOLT  STATION. 

of  the  stresses,  and  that  a  tie  could  be  so  designed  as  to  properly 
care  for  these  stresses  and  thus  prevent  the  breaking  down  of  the 
tie  in  the  manner  just  referred  to.  With  this  point  cared  for  the 
life  of  the  tie  would  be  greatly  prolonged. 

It  was  the  universal  opinion  of  track  men  that  through  the 
use  of  reinforced  concrete  ties  the  cost  of  maintenance  could  be 
materially  reduced  and  the  alignment  of  the  track  much  more 
readily  maintained.  It  is,  however,  on  curves  that  the  ties  are 
least  effective  and  their  Ufe  very  brief.  Another  objection  seems 
to  be  that  the  use  of  the  concrete  tie  usuallj^'  results  in  a  rigiditjr 


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of  roadbed  which  is  extremely  undesirable  from  an  operating 
point  of  view,  with  the  result  that  many  devices  have  been  tried 
with  a  view  to  introducing  some  elastic  medium  which  will  absorb 
the  shock  of  passing  locomotives. 

At  the  Exposition  in  Turin  were  shown  a  numl^er  of  rein- 
forced concrete  ties  with  wood  blocks,  fiber  cushions,  and  other 
similar  elastic  shock  al)sorbers,  placed  in  the  tie  with  a  view  to 
increasing  its  life.     In  most  cases  the  design  of  the  tie  seemed 


FIG.   8. — MANNER  OF  FAILURE  OF  REINFORCED  CONCRETE  TIES  IN  LONDON  AND 
SOUTHEASTERN   RAILWAY. 

to  be  at  fault;  many  of  them  had  been  developed  by  mechanics 
not  skilled  in  structural  designing,  with  the  result  that  the  rein- 
forcement was  not  properly  placed  with  regard  to  the  stresses, 
especially  those  of  impact;  and  it  appears  to  me  that  the  con- 
crete tie  problem  can  only  be  solved  with  a  due  consideration 
for  these  stresses. 

Every  one  of  the  railroad  officials  who  has  had  to  do  with 
concrete  ties  in  Europe  feels  sure  that  a  tie  will  be  developed 
which  will  overcome  the  objections  above  indicated  and  redyc^ 


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44  Annual  Address  by  the  President. 

the  initial  cost  to  a  point  where  its  life  and  reduced  cost  of  main- 
tenance will  make  it  the  cheapest  railroad  tie. 

The  objection  in  this  country  to  the  reinforced  concrete  tie, 
namely,  its  rigidity  under  moving  loads  and  the  consequent  objec- 
tionable hammering  to  the  locomotive,  can  be  cared  for  by  the 
introduction  of  an  elastic  cushion  in  the  shape  of  fiber  or  wood. 
I  believe  the  concrete  tie  will  be  the  tie  of  the  future  and  its  first 
cost  will  prove  of  minor  consideration  when  the  reduced  cost  of 
maintenance  and  durability  is  considered. 

Another  interesting  development  in  the  use  of  concrete  is  in 
connection  with  sewers  or  conduits  of  circular  or  elliptical  form 
in  which  the  walls  are  made  up  of  segments  of  concrete,  which 
after  being  placed  in  position  are  grouted  or  cemented  together, 
forming  a  solid  ring.  There  were  a  number  of  cases  where  unusual 
economy  had  been  effected  through  the  use  of  these  sewers.  In 
some  of  them  the  segments  were  grooved  along  the  axis  and 
around  the  circumference  in  which  the  reinforcement  was  placed. 

The  use  of  reinforced  concrete  for  the  lining  of  sewers  and 
tunnels,  in  my  opinion,  is  a  very  important  application.  The 
possibility  of  molding  these  blocks  and  placing  them  in  position, 
and  filling  the  space  between  the  roof  and  the  ring  with  con- 
crete forms  a  very  simple  and  effective  method  of  tunnel  lining, 
the  application  of  which  is  cheaper  than  brick  and  also  cheaper 
than  concrete  construction  where  tight  forms  must  be  constructed 
and  maintained  in  position  until  the  concrete  has  properly  hard- 
ened. In  the  segmental  method,  with  the  completion  of  the  ring, 
the  concrete  backing  may  be  readily  placed  in  position  and  but 
little  shoring  will  be  necessary  until  the  concrete  has  set. 

Another  extremely  interesting  matter  was  the  use  of  rein- 
forced concrete  pipe  of  varying  lengths  which  was  laid  as  shown 
in  Fig.  9  to  conform  to  the  general  contour  of  the  ground,  the 
connections  and  adjustment  being  effected  by  means  of  loose 
sleeves  slipped  aroimd  the  joints.  After  the  pipes  and  sleeves 
are  in  position  the  spaces  between  the  sleeves  are  grouted  solidly 
to  the  pipe  This  appUcation  is  in  advance  of  anything  we  are 
doing  in  this  country.  Sections  of  reinforced  concrete  pipe  laid 
in  this  manner,  in  lengths  of  12  feet  or  more,  would  have  great 
possibilities  for  use  in  pressure  lines.  The  pipe  in  the  illustration 
were  made  in  a  machine  not  unlike  a  lathe.     The  reinforcement 


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Was  placed  around  a  core  rotating  horizontally  and  a  very  stiff 
mortar  thrown  against  it.  After  the  mortar  had  been  built  out 
to  the  requisite  thickness,  the  pipe  was  wrapped  with  cotton 
bands  four  or  five  inches  in  width.  The  pipe  was  then  removed 
and  the  wrapping  kept  wet  until  the  mortar  had  set,  when  the 


1    % 

>.2  "^i 

A.4.  .' 

FIG.   9.- 


-REINFORCED  CONCRETE  PIPE  OF  VARYING  LENGTHS  IN  USE  IN 
SWITZERLAND. 


bands  were  pulled  off.  This  method  of  construction  naturally 
requires  a  great  deal  of  labor  and  even  if  considered  desirable 
would  be  entirely  too  expensive  for  use  in  this  country. 

Fig.  10  shows  a  cement  products  yard  in  Vienna  and  par- 
ticularly illustrates  the  concrete  ducts  which  are  being  used  in 


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Annual  Address  by  the  President. 


that  city.  These  ducts  have  longitudinal  recesses  in  which  rein* 
forcement  is  placed  and  the  remaining  space  filled  with  cement 
mortar;  this  stiffens  the  ducts  and  holds  them  in  .position.  It 
seemed  to  me  there  was  an  excellent  opportunity  for  this  type 
of  construction  in  this  country.  When  properly  cemented  in 
position,  the  ducts  formed  were  in  every  way  desirable  and  I  am 
told  that  the  cost  is  much  less  than  that  of  terra  cotta  or  other 
material. 

During  my  last  visit  in  Vienna  I  had  occasion  to  refer  to  the 
use  of  concrete  pavements  and. I  find  that  this  type  is  coming 


FIG.    10. — CEMENT    PRODUCTS   PI/ANT    OF    PITTEL    AND    BRAUSEWETTER    AND 
E.    GAERTNER   IN   VIENNA,    AUSTRIA. 

into  gradual  use.  The  pavement  inspected  on  my  previous  visit 
and  reported  to  you  two  years  ago  had  been  laid  four  or  five 
years  and  during  my  last  visit  I  found  these  concrete  roadways 
still  in  excellent  condition  and  that  they  had  not  been  repaired. 
The  city  of  Vienna  was  engaged  in  laying  considerable  yardage 
of  these  pavements,  especially  around  the  Royal  Palace.  This 
pavement  was  of  great  width  and  was  entirely  of  concrete.  I  am 
absolutely  convinced  of  the  durability  of  these  pavements  and 
repeat  what  I  have  stated  in  my  previous  address,  that  I  believe 
they  will  come  into  general  use. 


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The  tank  of  reinforced  concrete  in  use  at  the  coal  mines, 
in  Rotherham,  England,  to  remove  the  coal  dust  from  the  water 
coming  from  the  coal  washery  is  of  considerable  interest.  This 
water  is  pumped  into  the  tank,  the  coal  dust  is  removed  and 
the  clean  water  returned  to  the  washery.  This  coal  dust  is  used 
in  briquetting  coal.  Steel  tanks  are  not  available  for  this  purpose 
because  the  sulphur  in  the  coal  would  so  corrode  the  steel  as  to 
make  its  life  extremely  short.  The  concrete  tank  has  proved 
highly  satisfactory  not  only  in  its  resistance  to  the  action  of 
sulphur  but  in  its  water-tightness. 

I  commented  on  the  artistic  use  of  reinforced  concrete  in 
bridge  construction  in  my  previous  address,  but  the  matter  is 
so  striking  that  I  cannot  help  referring  to  it  again.     The  innum- 


FIG.   11. — BIEMORIAL  REINFOKCED  CONCRETE  BRIDGE  CONNECTING  HISTORICAL 
AND  ART  EXPOSITIONS  OVER  TIBER,   IN  ROME,   ITALY. 

erable  bridges  throughout  Europe,  carefully  designed,  carrying 
railroad  as  well  as  ordinary  highway  traffic,  are  monuments  to 
the  ability  of  the  European  engineer.  The  designs  are  for  the 
most  part  graceful  and  show  a  wide  diversity  in  artistic  treatment. 

A  structure  of  great  beauty  is  the  Memorial  Bridge  (Fig.  11) 
in  Rome  connecting  the  Historical  and  Art  Expositions,  located  on 
opposite  sides  of  the  Tiber.  This  bridge  was  built  by  the  Henne- 
bique  Construction  Company  and  is  an  example  of  European 
engineering  skill.  By  reason  of  floods,  it  was  necessary  to  con- 
struct the  centering  on  which  this  bridge  was  built,  of  reinforced 
concrete — ^which  is  unusual  and  the  first  application  of  the  use 
of  reinforced  concrete  for  centering  that  has  come  to  my  at- 
tention. 

The  bridge  has  a  span  of  100  meters  and  is  built  in  imitation 


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48  Annual  Address  by  the  tRBSil)ENt. 

of  the  native  Travertine  stone;  the  beauty  of  this  is  fully  as 
great  as  the  artificial  Travertine  stone  to  be  found  in  the  New 
York  station  of  the  Pennsylvania  Railroad.  This  structure  was 
built  by  the  Italian  government,  and  many  severe  tests  were 
applied  with  but  extremely  slight  deflections. 

The  manner  in  which  this  bridge  was  tested  is  also  of  interest. 
A  commission  was  appointed  to  conduct  the  tests  for  the  govern- 
ment. These  tests  consisted  in  moving  heavy  steam  rollers  and 
marching  soldiers  in  a  solid  mass  over  the  bridge;  particularly 
interesting  was  the  loading  of  the  bridge  solidly  with  soldiers 
and  studying  the  effect  of  their  cadenced  step  on  the  structure. 


FIG.  12. — REINFORCED    CONCRETE    TRUSS    113.8  FT.  SPAN    USED  IN  MAIN  RAILr 

ROAD  STATION  IN  LEIPSIC,  ERECTED  FOR  TESTING  IN  COSSEBAUDE, 

NEAR  DRESDEN,    GERMANY. 

I  think  it  may  be  stated  without  fear  of  contradiction  that 
reinforced  concrete  structures  properly  designed  are  less  affected 
by  vibratory  and  cadenced  loads  than  any  other  structure.  It 
is  particularly  noticeable  that  in  structures  of  identical  design 
as  to  carrying  capacity,  those  of  steel  show  more  movement  than 
those  of  reinforced  concrete. 

A  most  interesting  structure  is  the  truss  (Fig.  12)  erected 
initially  by  the  firm  of  Dyckerhoflf  and  Widman,  at  their  plant  in 
Dresden.    It  was  erected  for  testing  the  actual  strength  and  justify- 


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Annual  ADUREgd  by  fHE  President.  4§ 

ing  the  use  of  a  truss  of  this  tjrpe  in  the  main  railroad  station  in 
Leipsic.  The  arch  was  loaded  in  various  ways  and  the  deflections 
observed,  and  the  tests  were  so  satisfactory  that  it  was  successfully 
used  in  the  structure.  It  is  unusual  in  this  coimtry  to  go  to  the 
expense  of  erecting  a  structure  of  this  kind  and  applying  tests  in 
order  to  satisfy  the  officials  that  it  is  amply  safe;  It  would,  how- 
ever, be  an  effective  means  of  preventing  failures. 

A  matter  that  impressed  me  was  the  development  of  struc- 
tures, many  of  them  articulated,  composed  of  separately  molded 
parts,  and  the  views  herein  presented  exemplify  some  of  the  more 
remarkable  of  these  structures.  The  practice  of  casting  mem- 
bers and  then  pinning  them  together  and  encasing  the  connection 
in  concrete  is  a  development  that  seems  to  meet  with  favor,  and 
while  this  may  not  appeal  to  many  of  the  conservative  engineers 
of  this  country,  it  seems  to  me  that  when  this  pin  connection  is 
of  the  same  design  as  pin  connected  steel  members,  there  is  no 
reason  why  this  type  of  structure,  when  properly  designed,  should 
not  be  more  serviceable  by  reason  of  the  concrete  covering  which 
makes  it  more  durable  than  a  structure  of  steel.  The  concrete 
trestle  used  in  connection  with  the  mine  at  Floreiffe,  Belgium, 
the  lower  portion  of  this  is  used  for  the  county  roadway  and  the 
upper  portion  for  the  handling  of  cars  to  the  "tipple"  from  the 
coal  mine,  is  an  illustration  of  a  remarkable  development  of 
this  principle.  I  was  informed  that  the  parts  of  this  structure 
were  separately  molded  and  afterward  erected  in  place  in  a  very 
short  space  of  time  and  that  the  cost  was  considerably  less  than 
a  similar  structure  of  steel  or  of  timber.  There  is  a  tendency 
towards  systems  requiring  separately  molded  members,  and  it 
seems  to  me  that  such  systems  afford  an  opportunity  for  economy. 
The  weak  points  in  such  structures  are  the  joints,  and  with  the 
same  attention  to  these  connections  that  is  given  to  steel  struc- 
tures there  is  no  reason  why  the  joint  in  a  concrete  structure 
should  not  be  stronger  than  the  weakest  part  of  the  separate 
members. 

A  development  of  the  Visintini  system  was  to  me  somewhat 
surprising,  since  this  system  is  very  little  used  in  this  country; 
the  early  attempts  to  introduce  it  were  unsuccessful,  chiefly 
because  of  its  cost  as  compared  with  that  of  other  systems  of 
reinforced  concrete  construction.     In  Europe  it  has  a  wide  appli- 


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50  Annual  Address  by  the  President. 

cation  for  buildings  and  bridges.  Fig.  13  shows  the  bridge 
being  erected  in  Copenhagen,  Denmark,  with  girders  of  system 
Visintini.  This  bridge,  erected  in  connection  with  the  new  sta- 
tion that  the  State  Railways  were  building,  carries  a  street  with 
two  Hues  of  electric  trams  over  the  railroad.  The  ornamental 
portion  is  entirely  of  molded  concrete  which  was  not  subsequently 
treated.  Where  labor  is  inexpensive  the  cost  of  forms  is  not  so 
important  as  the  cost  of  material.  In  this  country,  where  condi- 
tions are  just  the  reverse,  this  system  proves  uneconomical.  The 
bridge  consists  of  deep  girders  spanned  by  beams  all  of  the  Visin- 
tini system.  The  latter  spaced  solidly  so  as  to  form  a  slab,  under 
the  railroad  tracks  and  20  inches  apart  between  the  tracks.     I 


FIG.    13. — HUmWAY  BRIDCIK   OF  REINFORCED   CONC^RETE   OVER  STATE    RAILWAY 
TRACKS,    COPENHAGEN,    DENMARK. 

think  this  bridge  might  be  said  to  be  a  type  of  unit  construction. 
Certainly  the  bridge,  which  was  nearly  completed,  presented  an 
extremely  beautiful,  ornamental  appearance  and  far  more  desir- 
able than  a  similar  structure  of  steel.  I  believe  that  this  method 
of  construction,  which  is  in  a  measure  illustrated  in  the  flat  slab 
construction  in  use  in  railroad  bridges  in  this  country,  possesses 
great  possibilities  in  the  matter  of  appearance  and  speed  of  erec- 
tion. All  the  beams  of  the  system  could  be  molded  and  the 
structure  then  erected  continuously,  replacing  perhaps  an  old 
structure,  without  interfering  with  the  traffic. 

An  interesting  type  of  girder  construction  is  shown  in  Fig.  14, 
a  highway  bridge  at  Desna,  Austria,  which  consists  of  a  series  of 
Visintini  girders  supported  on  piers  of  rather  unusual  construction. 


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The  application  of  this  system  for  arch  ribs  of  a  building  is  illus- 
trated in  (Fig.  15)  the  ceiling  of  a  church  erected  in  Aussig, 
Austria,  and  which  I  think  is  also  an  application  of  unit  system. 
The  lower  flange  of  the  rib  of  the  arch  is  extended  so  as  to  support 
the  Visintini  beams  which  form  the  ceiling.  Another  type  of 
structure  which  shows  a  trend  in  Europe  that  conservative  struc- 
tural engineers  in  this  country  might  call  dangerous  is  illustrated 
Fig.  16.  This  is  a  trussed  bridge  practically  a  development  of 
the  Visintini  system,  which  forms  a  central  span,  with  Visintini 
girders  and  beams  used  in  the  approaches. 


FIG.    14. — REINFORCED   CONCRETE    HIGHWAY   BRIDGE,  DESNA,  AUSTRIA. 

The  photograph,  Fig.  17,  shows  the  coal  bunkers  of  the 
extensive  plant  of  the  city  gas  works  in  Vienna.  The  one  on 
the  left  side  has  most  of  the  forms  removed  and  illustrates  the 
generally  pleasing  character  of  the  structure,  which  is  notable  in 
view  of  the  fact  that  it  must  be  massive,  in  order  to  carry  a  large 
quantity  of  coal.  The  attempt  to  render  this  structure  pleasing 
and  ornamental  could  well  be  emulated  by  our  American  designers. 
The  exterior  surface  is  dressed  with  pneumatic  tools  and  a  color 
effect  has  been  obtained  which  is  not  unlike  that  attained  in  the 
construction  of  the  Connecticut  Avenue  Bridge  in  Washington. 
D.  C. 


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52 


Annual  Address  bv  thE  President* 


no.    15. — PORTION  REINFORCED  CONCRETE  ROOF  OF  CHURCH,  AUSSIG,  AUSTRIA. 


FIG.    16. — REINFORCED    CONCRETE    TRUSS    HIGHWAY    BRIDGE     NEAR    VIENNA, 

AUSTRIA. 


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53 


We  have,  of  course,  many  water  towers  in  this  country,  but 
the  thing  that  most  impresses  me  in  connection  with  those  in 
European  countries,  is  the  thinness  of  the  tank  walls  and  the 
fact  that  they  are  constructed  without  the  aid  of  waterproofing; 
the  density  of  the  concrete  and  the  manner  of  reinforcing  is  suf- 
ficient to  so  distribute  the  cracks  as  to  render  them  water-tight. 

In  connection  with  buildings  abroad  it  would  seem  that  more 
attention  is  given  to  the  exterior  and  interior  finish,  even  in 
factory  buildings,  than  is  given  in  this  country;  the  skill  used  in 


FIG.   17. — REINFORCED  CONCRETE  COAL  BUNKERS,  CITY  GAS  WORKS,  VIENNA. 

secimng  a  pleasing  finish,  even  considering  the  low-priced  labor 
of  Europe,  is  very  rarely  more  expensive  than  the  rough  finish 
commonly  used  here.  The  tendency  toward  flat  slabs  and  the 
elimination  of  as  many  beams  as  possible  shows,  I  believe,  an 
unmistakable  turn,  which  is  reflected  in  this  country  in  the  recent 
development  of  the  flat  slab  type  of  construction.  In  many 
places  the  elimination  of  beams  results  in  paneled  effects  through 
the  use  of  girders  between  the  columns  and  mortising  and  mold- 
ing the  connection  between  the  slab  and  girder  in  such  a  way 
as  to  produce  pleasing  ornamental  effects.     There  is  also  a  ten^ 


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54 


Annual  Address  by  the  President. 


dency  to  panel  the  slab  itself,  which  relieves  its  flatness  and  adds 
no  little  to  the  beauty  of  the  interior  finish.  The  use  of  much 
higher  ceilings  than  are  commonly  used  in  this  country  renders 
flat  slabs  unnecessary  for  the  distribution  of  light.  The  effect 
of  the  paneling  is  somewhat  that  of  the  Roman  barrel  arch,  and 
this  latter  type  of  construction  may  be  seen  in  the  ceiling  decora- 
tion of  many  European  structures. 

An  excellent  exterior  finish  having  the  appearance  of  gray 
stone  was  to  be  seen  in  the  C'igarette  Paper  Factory  in  Vienna. 
This  structure  had  been  erected  many  years  and  the  weathering 
had  been  so  uniform  as  not  to  in  any  way  mar  its  beauty.  This 
building  was  illustrated  in  my  address  describing  my  trip  of  two 


iiillri 


111. 
liiUjiiiliii  fliirrn 


111 

Mi 

iii 
nil 


FIG.    18. — TRADE  SCHOOL  OF  REINFORCED  CONCRETE,   VIENNA,  AUSTRIA. 

years  ago  and  is  again  referred  to  because  after  an  interval  of  two 
years  the  exterior  finish  of  the  building  remains  unchanged.  The 
entire  ornamentation  is  of  concrete  and  serves  as  an  excellent 
illustration  of  the  artistic  possibilities  of  this  material. 

The  Trade  School  in  Vienna  (Fig.  18)  is  also  an  excellent 
example  of  the  artistic  treatment  of  concrete.  The  paneling  and 
ornamental  work  are  most  excellent  in  character,  and  for  this 
reason  do  not  call  forth  the  criticism  which  once  was  so  rife  in 
this  country,  where  the  crude  structures  which  we  erected  left 
much  to  be  desired  from  the  aesthetic  point  of  view.  It  is  fre- 
quently the  practice  in  Europe,  especially  in  Vienna,  to  cast 
monolithic  walls  and  tool  them  afterwards,  in  a  manner  to  pro- 


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duce  the  effect  of  stone.  This,  however,  does  not  appeal  to  me 
so  strongly  as  the  structure  in  which  there  is  no  attempt  to 
imitate  stone,  but  where  the  material  is  used  to  stand  for  what 
it  is,  producing  pleasing  ornamentation  and  a  surface  uniform 
in  color  and  texture  and  free  from  those  stains  and  cracks  which 
are  frequently  seen  in  structures  of  concrete  in  this  country. 


FIG.    19. — CITY  HALL  OF  REINFORCED  CONCRETE,  NEAR  BADEN,    AUSTRIA. 

Fig.  19  is  a  view  of  the  City  Hall  at  Weikersdorf  near  Baden, 
Austria.  The  entire  wall,  with  ornamentation,  is  of  concrete 
without  any  attempt  to  imitate  other  material,  which  I  think 
illustrates  that  this  is  the  proper  way  in  which  to  use  concrete 
and  that  when  so  used  the  results  are  much  more  effective  than 
where  it  is  used  in  imitation  of  other  materials. 

A  favorite  form  of  exterior  decoration  is  to  apply  phvster 


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Annual  Address  by  the  PREsroENT. 


to  the  rough  concrete  and  mold  it  in  a  manner  to  produce  artistic 
effects. 

The  photograph  of  the  Villa  Figari  in  Genoa,  Italy,  shown 
in  Fig.  20,  is  an  illustration  of  the  splendid  possibilities  in  the 
artistic  use  of  reinforced  concrete.  This  graceful,  beautiful  struc- 
ture needs  no  comment.  The  erection  of  this  Villa  involved  a 
number  of  interesting  problems  iVi  design  which  I  think  were  met 


FIG.    20. — VILLA   FIGARI,    GENOA,    ITALY. 

more  successfully  through  the  use  of  this  material  than  would  be 
possible  through  the  use  of  any  other.  There  are  a  number  of 
plants  in  this  country  engaged  in  making  ornamental  concrete 
products  of  a  very  high  order,  and  fully  equal  to  some  of  the 
best  work  done  in  Europe,  but  the  American  designer  does  not  at 
the  present  time  seem  to  appreciate  the  adaptability  of  concrete 
for  use  in  the  ornamental  structural  portions  of  buildings;  it 
seems  to  me  that  development  along  the  lines  illustrated  in  the 
Villa  Figari  opens  a  wonderfully  promising  field. 


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As  the  architect  and  designing  engineer  more  fully  realize 
the  architectural  possibilities  of  concrete  and  apply  them  in  build- 
ing construction  with  a  due  appreciation  for  the  aesthetic,  there 
will  result  such  graceful  structures  as  will  entirely  meet  the 
criticisms  and  objections  to  the  many  cumbersome,  ungraceful 
and  unattractive  structures  which  are  being  erected  at  the 
present  time. 

The  desire  to  render  even  ordinary  structures  beautiful  is 


FIG.   21. — REINFORCED    CONCRETE    CAR   BARNS   OF    CITY    OF   VIENNA,    AUSTRIA. 

particularly  observable  in  Europe  and  it  is,  therefore,  unusual 
to  see  even  a  mill  building  in  which  no  attempt  has  been  made 
to  give  it  a  proper  finish.  The  eye  for  the  beautiful  is  a  matter 
of  education  and  growth  and  I  presume  that  in  time  we  will 
develop  similar  tastes  so  that  our  mill  buildings  will  be  given 
artistic  finishes.  It  should  be  borne  in  mind,  however,  that  the 
cost  of  this  work  in  Europe  is  considerably  less  than  in  this 
country,  by  reason  of  the  cheap  labor  and  because  of  the  greater 
quantity  that  is  done;  they  have  acquired  more  skill  and  there 


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58  Annual  Address  by  the  President. 

are  a  great  many  more  skilled  men  capable  of  doing  this  class 
of  work. 

The  car  barns  of  the  city  of  Vienna,  shown  in  the  illustration 
(Fig.  21),  is  another  development  in  the  use  of  concrete  which 
I  think  will  become  general  in  the  future.  This  structure  is  built 
entirely  of  concrete,  including  the  roof  which  has  not  been  water- 
proofed. I  understand  that  the  cost  of  this  structure  was  mate- 
rially less  than  the  cost  of  other  types  of  construction.  The 
span  and  lines  of  the  girder  was  a  matter  of  interest  and  is  char- 
acteristic of  the  skill  of  the  Austrian  engineer. 

A  building  of  reinforced  concrete  which  was  brought  to  my 
attention  during  my  visit  two  years  ago,  and  which  was  then 
under  construction,  is  the  Urania  Building  in  Vienna,  which  is 
devoted  to  the  development  of  popular  musical  education.  It 
has  a  rather  difficult  problem  in  acoustics  which  is  of  moment 
to  those  interested  in  concrete.  The  main  auditorium  has  a  floor 
and  ceiling  of  reinforced  concrete  of  considerable  thickness; 
above  and  below  this  auditorium  are  smaller  halls  for  musical 
entertainment.  The  large  auditorium  contains  an  organ,  and 
there  is  no  connection  between  it  and  the  halls  above  and  below, 
yet  the  Director  states  that  when  there  is  a  concert  in  progress 
in  the  large  auditorium  it  is  impossible  to  hold  a  concert  in  either 
of  the  other  auditoriums,  because  the  sound  of  the  music  in  the 
large  hall  is  so  pronoimced  as  to  seriously  interfere  with  the  per- 
formance in  the  other  halls.  This  subject  has  received  a  great 
deal  of  consideration  in  Vienna  and  methods  are  now  in  progress 
to  eliminate,  if  possible,  by  some  insulating  medium,  the  trans- 
mission of  sound. 

Another  matter  of  interest  was  the  work  which  the  Austrian 
Association  is  doing  in  investigations  and  tests,  not  unlike  those 
of  our  own  Committee  on  Reinforced  Concrete,  except  that  the 
value  of  the  work  accomplished  is  greater  because  the  work  is 
much  more  extensive.  They  have  conducted  a  comprehensive 
series  of  tests  of  columns  and  beams,  the  cost  of  the  work  being 
defrayed  by  the  Austrian  cement  manufacturers,  and  has  been 
under  the  auspices  of  representatives  of  the  government,  the 
Society  of  Engineers  and  Architects,  the  Austrian  Concrete  Asso- 
ciation and  the  Austrian  Association  of  Cement  Manufacturers. 
The  principal  feature  of  the  tests  which  were  being  conducted  at 


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the  time  of  my  visit  was  a  study  of  the  effect  of  the  weight  of 
wall  in  restraining  the  ends  of  beams;  a  number  of  different 
methods  were  being  tried  and  it  had  been  found  that  the  stiff- 


PIG.  22. — A  RESTRAINED  REINFORCED  CONCRETE  BEAM  AFTER  TESTING. 


FIG.   23. — METHOD    OF    APPLYING    LOAD    IN    TESTING    REINFORCED    CONCRETE 

BEAMS. 

noss  of  the  beam  was  materially  increased  through  the  weight 
of  the  wall. 

Fig.  22  illustrates  one  of  these  beams  after  test.     In  some 


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60  Annual  Address  by  the  President. 

cases  the  beam  rested  on  a  pier,  and  in  others  it  extended  over; 
in  still  others  it  was  imbedded  in  concrete,  or  laid  up  in  a  brick 
wall  so  as  to  approximate  practical  conditions. 

Fig.  23  shows  the  manner  of  loading  and  observing  the  deflec- 
tions. The  method  of  applying  the  load  is  perhaps  of  interest. 
The  load  to  be  apphed  was  carried  by  hydraulic  jacks,  the  lower- 
ing of  which  brought  the  weight  of  this  super-imposed  load  on 
the  beam. 

One  thing  that  was  apparent  on  my  recent  trip,  and  which 
must  be  a  matter  of  great  gratification  to  every  member,  is  the 
high  regard  in  which  this  Association  and  its  work  are  held  in 
Europe.  It  is  taken  generally  as  a  model,  and  in  many  cases 
the  character  of  the  work  done  here  and  the  value  of  its  pro- 
ceedings and  discussions  are  so  appreciated  as  to  result  in  a 
number  of  Europeans  becoming  members  in  order  to  secure  its 
publications. 

There  is  also  a  cordial  feeling  of  cooperative  good-will  between 
the  various  concrete  organizations  of  Europe  and  our  Association, 
which  I  hope  may  be  fostered  and  that  it  may  be  possible  through 
the  interchange  of  delegates,  papers,  and  in  other  ways,  to  extend 
this  cordiality  so  as  to  obtain  the  advantages  of  the  development 
in  the  art  of  concrete  construction  in  various  parts  of  the  world. 

This  Association  stands  for  education  in  the  development 
of  the  proper  use  of  concrete,  and  certainly  it  should  be  a  part 
of  its  policy  to  encourage  international  co-operation,  to  the  end 
that  the  development  in  this  country  may  proceed  with  a  full 
knowledge  of  what  is  being  done  by  our  foreign  competitors. 


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REPORT  OF  THE  COMMITTEE  ON  REINFORCED 
CONCRETE  AND  BUILDING  LAWS. 

In  accordance  with  the  program  of  tests  on  completed 
stnictures  presented  to  the  Association  at  the  last  convention, 
four  tests  have  been  made,  two  of  them  on  standard  forms  of 
reinforced  concrete  floors  in  which  the  concrete  slab  is  supported 
by  one  or  more  intermediate  beams  which  in  turn  are  framed 
into  or  supported  by  girders  carrying  the  load  to  the  columns. 
Of  the  other  two  tests  one  is  on  the  girderless  or  flat  slab  floor, 
and  the  other  on  a  combination  of  tile  and  concrete  floor,  in  which 
the  reinforcement  is  placed  in  two  directions. 

Making  arrangements  for  the  tests*  and  computing  the 
results  have  taken  up  all  the  available  time  of  the  Conmiittee; 
the  test  data  is  therefore  presented  to  the  Association  without 
any  attempt  at  generalization. 

The  tests  on  the  Wenalden  and  the  Turner-Carter  buildings 
were  made  under  the  direct  supervision  of  A.  N.  Talbot;  the 
other  tests  were  made  by  F.  J.  Trelease  of  the  Research  Depart- 
ment of  the  Corrugated  Bar  Company,  with  the  assistance  of 
W.  A.  Slater  of  the  Illinois  Engineering    Experiment  Station. 

Part  I.    Tests  op  Two  Reinforced   Concrete   Buildings 
OF  the  Beam  and  Girder  Type. 

Preliminary, — These  tests  were  undertaken  for  the  purpose 
of  obtaining  information  on  the  action  of  the  composite  structure 
of  concrete  and  steel  under  load  in  a  reinforced  concrete  building 
constructed  under  the  usual  conditions  of  work.  Many  tests 
have  been  made  of  separate  reinforced  concrete  members,  but 
little  attention  has  been  given  to  the  measurement  of  stresses  and 
deformations  in  the  completed  building  and  to  the  determination 
of  their  actual  amount  and  distribution  and  of  the  effect  of  one 
part  of  the  structure  upon  another.  Load-deflection  tests  are 
common  and  are  of  value  in  judging  of  the  quality  of  workman- 
ship and  in  giving  confidence  in  the  structure,  but  they  throw 
littie  light  on  the  stresses  developed  in  the  different  parts  or 

(61) 


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62       Report  of  Committee  on  Reinforced  Concrete. 

upon  their  distribution.  A  variety  of  views  have  been  advanced 
on  the  relation  between  the  bending  moment  at  a  section  at  the 
support  and  that  at  the  middle  of  the  beam,  on  the  amount  of 
arch  action  which  may  be  developed  in  the  structure,  on  the  dis- 
tribution of  the  stresses  across  a  floor  slab  acting  as  the  flange 
of  a  T-beam,»on  the  restraint  of  girders  and  beams,  etc.  These 
tests  were  undertaken  in  an  effort  to  obtain  some  information 


FIG.    1. — INSTRUMENTS    AND   TOOLS. 

on  such  matters  as  well  as  to  find  something  of  the  general  action 
of  reinforced  concrete  structures  as  a  whole. 

The  general  method  of  test  followed  the  plan  outlined  by 
Arthur  R.  Lord  in  the  paper,  A  Test  of  a  Flat  Slab  Floor  in  a 
Reinforced  Concrete  Bxdlding*  presented  at  the  New  York  Con- 
vention. Holes  were  cut  in  the  concrete  until  the  reinforcing 
bars  were  bared.  Gauge  holes  were  then  drilled  in  these  bars, 
at  distances  apart  to  give  the  proper  gauge  lengths.  Where 
measurements  of  deformation  of  the  concrete  were  desired,  holes 
were  cut  in  the  concrete  and  a  metal  plug  inserted  in  which  the 

♦  See  Proceeding,  Vol.  VII,  p.  156. 


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Report  op  Committee  on  Reinforced  Concrete.       63 

gauge  holes  were  later  drilled.  These  gauge  lines  were  selected 
in  places  where  it  was  thought  that  critical  stresses  would  be 
determined.  In  some  places  for  one  reason  or  another  the  rein- 
forcing bars  were  inaccessible  and  it  was  impracticable  to  obtain 
measurements  to  give  information  which  would  have  been  of 
interest.     In  some  cases  a  series  of  gauge  lines  were  used  to  de- 


/>-o/T»   C  rt>  //." 


Central  ho/^ 


Eccentric  hole  

Finishing 
tooL 

FIG.  2. — SHOWING  EXTEN80METER  AND  GAUGE  HOLES. 


termine  the  change  of  stress  or  distribution  from  one  point  to 
another  as  at  the  end  of  a  restrained  beam  and  across  the  floor 
slab  between  beams. 

The  measurements  were  made  by  means  of  Berry  exten- 
someters  of  the  form  developed  at  the  University  of  Illinois.  The 
extensometer  is  shown  at  the  bottom  of  Fig.  1.     The  instrument 


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64       Repor*  of  Committers  on  Reinforc*sd  CoNCRETti. 

reads  to  Wajf  in.  and  is  estimated  to  TJi^nis  in.  Its  make-up  is 
shown  in  Fig.  2,  as  are  the  gauge  holes.  In  making  a  measurement 
the  legs  of  the  instrument  are  inserted  in  the  gauge  holes,  a  read- 
ing taken,  the  instrument  taken  out  and  again  inserted  and  read, 
and  this  proceeding  repeated  until  a  number  of  readings  without 
serious  discrepancies  are  found.      The  operation  of  making  a 


FIG.  3. — TAKING   AN  OBSERVATION. 

measurement  is  shown  in  Figs.  3  and  4.  The  instrument  is  of 
a  simple  character,  but  its  use  requires  unusual  care  and  skill  on 
the  part  of  the  manipulator.  The  method  of  using  the  instrument 
as  well  as  the  necessary  general  conditions  attending  such  tests 
are  comprehensively  discussed  in  the  paper  presented  at  this 
convention  by  W.  A.  Slater  on  Tests  of  Reinforced  Concrete  Build- 
ings  under  Load.* 

Acknowledgment. — ^These  tests  were  undertaken  through  the 

*  See  page  168.— Ed. 


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65 


eflforts  of  the  Committee  on  Reinforced  Concrete  and  BuUding 
Laws  of  the  Association,  in  co-operation  with  the  Engineering 
Experiment  Station  of  the  University  of  Illinois.  The  money 
to  defray  the  expense  of  the  test  was  arranged  for  by  the  Presi- 
dent and  Treasurer  of  the  Association.  The  contractors  for  the 
two  buildings  co-operated  in  the  tests.  The  technical  part  of 
making  the  tests  was  done  by  members  of  the  staff  of  the  Engineer- 
ing Experiment  Station  of  the  University  of  Illinois. 


PIG.   4. — TAIONG   AN  OBSBBVATION. 

Comments, — ^A  few  words  on  the  basis  and  limitations  of 
such  tests  may  not  be  out  of  place.  The  measurements  and  ob- 
servations are  subject  to  some  uncertainty;  they  are  not  exact 
or  precise — some  erratic  readings  must  be  expected.  The  measur- 
ing instrument  is  used  under  unfavorable  conditions.  The  gauge 
holes  are  deep  in  the  concrete  and  the  measurements  may  be 
interfered  with  by  dust  or  other  obstructing  matter.  Great  care 
and  much  skill  is  necessary  in  making  observations.  Each  test 
of  this  kind  made  has  shown  advances  in  accuracy  and  certainty^ 


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66       Report  of  Committee  on  Reinforced  Concrete. 

and  further  experience  ought  to  show  further  progress.  It  must 
be  understood  that  the  structure  itself  is  not  entirely  homogeneous 
and  that  all  parts  of  it  do  not  act  alike.  Further,  the  structure 
itself  is  tied  together  so  closely  that  stress  in  one  portion  may  be 
modified  or  assisted  by  another  portion  which  may  not  be  thought 
to  afifect  it,  and  this  in  an  unknown  amount.  The  modulus  of 
elasticity  of  the  concrete  in  the  structure  may  not  be  known. 
The  load-deformation  lines  may  be  irregular  and  imperfect.    This 


r 


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■*2?i £2  URUBtSi EESfSSiS!  EH  !!!!&  ^ 
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^n  pti«  Iff  if  fffp  pfF  IB"  fvn  im  nn  M I      ^ 


FIG.    5. — THE   WENALDEN   BUILDING. 

all  means  that  care  must  be  taken  in  the  interpretation  of  results. 
Important  information  will  be  brought  out  by  such  tests,  as  these 
tests  show,  and  tests  of  special  features  of  construction  and  an 
accumulation  of  data  on  the  action  of  the  structure  as  a  whole 
will  be  worth  many  times  the  cost  of  the  work. 

Wenalden  Building  Test. 

Building, — The  Wenalden  Building,  Fig.  5,  is  a  ten-story 
reinforced  concrete  structure  at  18th  and  Lumber  Streets,  Chicago. 


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Report  of  Committee  on  Reinforced  Concrete.       67 

It  was  built  by  the  Ferro-Concrete  Construction  Company, 
Cincinnati,  Ohio,  in  accordance  with  the  plans  and  specifications 
of  Howard  Chapman,  architect.  It  is  now  occupied  by  Carson, 
Pirie,  Scott  and  Company,  dry  goods  merchants,  as  a  warehouse. 


Elevation  of  Intermediate  Beam. 


Elevation  of  Column  Beam. 


ri^iri^^:i^4;!a 


View  of  Girder. 

Fia.   6. — GENERAL  POSITION  OP  REINFORCEMENT. 

The  building  is  of  the  beam  and  girder  type.  The  floor  panels 
are  15  ft.  by  20  ft.  The  girders  are  placed  between  columns  in 
the  short  direction.  Floor  beams  extend  the  long  way  of  the  panel, 
there  being  two  intermediate  beams  built  into  and  supported  by 
the  girders  and  a  column  beam  built  into  and  supported  by  the 


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84       Report  of  Committee  on.  Reinforced  Concrete. 


if^.,4,ij^fer-^',^^-,4^^ 


II* 


// 


k 


I! 


I 


I 


'I    I 
r 


^.1 


8L-— L-.^ ^-— IJ 


□ 


in 


i 


^ij u u — ' — u u u ir^ 

FIG.  17.— PLAN  SHOWING  LOCATION  OF  GAUGE  UNES  ON  UNDER  SIDE  OF  FLOOR. 


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Report  op  Committee  on  Reinforced  Concrete.       85 


1 


i  11 


i^  1^  '*A  a44a  ^^a:  ■»  j*»^ 


^  a 


I 


I 


rn 


S"?! 


rt 


^ 


jAV 


— u u — 

FIO  18. — ^PLAN  8H0WIN0 


— u u u u \r^ 

LOCATION  OF  GAUGE  UNES  ON  X7PPBB  BIDE  OF  FLOOB. 


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86       Report  of  Committee  on  Reinforced  Concrete. 

Preparation  for  the  Test — ^A  week  was  used  in  preparing  for 
the  test.  Platforms  supported  by  scafifolding  for  the  use  of 
observers  were  built  on  the  second  floor.  Independent  of  this 
was  a  framework,  which  was  supported  by  the  second  floor,  for 
use  in  making  measurement  of  deflections.  The  boxes  for  hold- 
ing the  sand  were  constructed,  this  being  facilitated  by  a  power 
saw  located  on  the  second  floor.  Considerable  time  was  con- 
sumed in  drilling  holes  in  the  concrete  to  bare  the  reinforcement. 


p^J^^^^J^^u, 


I  L 


-!fr-J    - 


FIG.  19. — LOCATION  OF  SAND  BOXES  AND  FLOOR  CRACKS. 

In  some  cases  this  was  found  to  be  at  a  considerable  depth  from 
the  surface.  In  all  nearly  two  hundred  holes  were  cut  in  the  con- 
crete. Holes  were  drilled  in  the  reinforcing  bars,  as  heretofore 
described,  for  use  as  gauge  points.  The  gauge  length  was  made 
8  in.  The  position  of  the  gauge  lines  for  the  reinforcing  bare 
is  shown  on  Figs.  17  and  18  by  the  even  numbers.  For  use  in  the 
measurement  of  deformations  of  the  concrete,  holes  about  \  in. 
in  diameter  and  1  in.  deep  were  drilled  in  the  concrete  and  steel 


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Report  of  Committee  on  Reinforced  Concrete.        87 


FIG.  20.— VIEW  OP  SAND  BOXES. 


ip--»'»f 


FIG.   21. — ^VIEW   OF  TEST  LOAD  IN  TURNER-CARTER  BUILDING. 


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88       Rbpokt  op  Committee  on  Reinfobced  Concrete. 


^00 
None  ^     0 


I 

O     ^     Ok     ^     ^     ^      ^      _.        .      _       ^      _, 


%%%%%_%%%%% 


no.  22. — LOAD  DEFORMATION  DIAGRAMS  FOR  UNDER  BIDE   OF  BEABC8   AT  END. 


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Report  of  Couuhtee  on  Reinforced  Concrete.       89 


Ahne 


Do/or-ma'f'lon  p^rUnti'  o, 


^  =>  §  5  ^  S  S 
i  ^  S  §  §  § 


no.  23.— LOAD  DEFORMATION  DIAGRAMS  FOR  UNDER  SIDE  OF  BEAMS   AT  END. 


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90        Report  op  Committee  on  Reinforced  Concrete. 

plugs  were  inserted  and  set  in  plaster  of  Paris.  Gauge  holes 
for  receiving  the  points  of  the  extensometers  were  drilled  in  these 
plugs  with  a  No.  54  drill.  The  position  of  the  gauge  lines  is  shown 
in  Figs.  17  and  18  by  the  odd  numbers.  The  gauge  length  was 
Sin. 

The  deflections  were  measured  between  a  steel  ball  set  in 
the  under  surface  of  the  beam  and  a  ball  attached  to  the  frame- 
work previously  described.  The  measurements  were  made  by 
means  of  the  micrometer  shown  in  Fig.  1. 

Method  of  Loading. — The  test  area  was  on  the  third  floor. 
The  loading  material  was  damp  sand  which  was  placed  in  bot- 
tomless boxes.  These  boxes  were  of  various  sizes  and  were  placed 
in  such  a  way  as  to  give  a  well  distributed  load.  The  general 
size  of  the  box  was  4  ft.  6  in.  wide,  8  ft.  long  and  4  ft.  6  in.  deep. 
Fig.  19  shows  the  position  of  the  boxes  and  the  test  area.  Fig. 
20  is  a  view  with  the  sand  boxes  ready  for  loading.  The  boxes 
were  made  small  enough  to  permit  a  good  distribution  of  load 
even  though  part  of  the  weight  of  the  sand  might  be  carried  by 
arching  and  friction  down  the  sides.  The  test  area  covered  three 
full  panels  and  parts  of  four  others,  in  all  equivalent  to  five  panels. 
A  loading  space  was  chosen  which  it  was  thought  would  give  the 
fullest  stresses  over  the  girders  and  beams  on  which  the  principal 
measurements  were  made.  In  removing  the  load  the  outer  panels 
were  unloaded  first  in  an  attempt  to  determine  the  relation  be- 
tween single  panel  loading  and  group  loading.  The  load  applied 
was  the  equivalent  of  300  lb.  per  sq.  ft.,  double  the  design  live 
load. 

Before  beginning  the  test,  a  calibration  of  the  heaviness  of 
the  sand  was  made  by  weighing  the  sand  which  had  been  shoveled 
into  a  box  of  16  cu.  ft.  capacity  placed  on  the  scales.  It  was 
found  that  there  was  a  difference  of  about  10  per  cent,  in  the  weight 
of  sand  which  had  been  thrown  in  loosely  and  sand  which  was 
packed  somewhat.  During  unloading,  the  entire  contents  of 
three  of  the  sand  boxes  (about  500  cu.  ft.)  were  weighed.  This 
gave  an  average  of  88.6  lb.  per  cu.  ft.,  agreeing  closely  with  the 
weights  of  the  unpacked  sand  previously  weighed,  and  this  value 
was  used  in  the  calculation  of  loads. 

On  a  part  of  the  area  where  the  boxes  were  not  carried  to 
a  suflicient  height  and  where  the  space  was  not  covered  adequately 
by  them,  cement  in  sacks  was  used  as  loading  material. 


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Report  of  Committee  on  Reinforced  Concrete. 


91 


The  supply  of  sand  for  the  loading  had  previously  been  de- 
livered on  the  same  floor,  the  piles  being  kept  at  least  one  panel 
away  from  the  location  of  the  test  area,  and  this  was  distributed 
over  sufficient  floor  space  that  the  stresses  in  the  beams  of  the 
test  area  could  not  be  affected.  In  applying  the  load  the  sand 
was  wheeled  in  barrows  and  dumped  into  the  boxes.  As  the 
sand  was  placed,  the  sides  of  the  boxes  were  rapped  to  break  the 
adhesion  of  the  sand.     Some  leveling  of  the  sand  in  the  boxes 


Abne 

None  ^     0 

^aoo 


I 


^200 


125 


Qi    15   JVi 


I 


£i}L 


\ 


\ 


ZM 


^| 


2J3 


FIG.   24. — ^LOAD  DEFORMATION   DIAGRAMS  FOR  UNDER   SIDE   OF  BEAMS  AT  END. 

was  done,  but  there  was  little  compacting  by  tramping  or  other- 
wise. 

Making  the  Test, — A  very  important  element  of  a  test  of 
this  kind  is  the  initial  observation  for  fixing  the  zero  point  of  the 
test  readings.  Three  sets  of  observations  for  a  number  of  gauge 
lines  were  made  before  the  beginning  of  the  test,  on  the  after- 
noon of  September  10  and  the  forenoon  of  September  11. 
Where  discrepancies  were  found  new  observations  were  made. 
Even  with  this  number  of  observations  there  are  uncertainties 


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92       Report  of  Committee  on  Reinforced  Concrete. 


Mono 


zSOO 


^00 


£ 
\AII  ^200 

\aii  \/oo 


0^ 


^^00 

^  )EFHt  \dO0 

\Af/  ^2O0 

v%w'^     0 

£    ^300 

\£diH^300 

\KrHi  ^00 

^All   ^300 

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5 


3*4 


31 Z 


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1 


390 


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§    ^    «     >     -    «    «     ^ 


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&«     b 


X 
B 


FIG.   25. — ^LOAD  DEFORMATION  DIAGRAMS  FOR  UPPER  SIDE   OF  BEAMS  AT  END. 


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Repokt  op  Committee  on  Reinfokced  Concrete.       93 

in  some  initial  readings.  Experience  confirms  the  view  that 
before  any  load  is  placed  the  initial  readings  which  have  been 
taken  should  be  worked  up  and  observations  repeated  untiT  all 
discrepancies  and  uncertainties  have  been  removed. 

Readings  were  taken  immediately  after  the  completion  of  each 


if    ^00 

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£     ^^OO 

£    ^300 
\£6iH^^300 

\defhi  ^O 


'AH 


^AH   ^2tt? 


nQ.26. — ^LOAD  DEFORMATION  DIAGRAMS  FOR  UNDER  SIDE  OF  BEAMS  AT  MIDDLE. 

increment  of  load  and  again  immediately  before  the  beginning 
of  placing  another  increment  of  load.  This  usually  corresponded 
with  evening  readings  and  morning  readings.  A  series  of  readings 
was  also  taken  with  the  full  test  load  on.   These  extended  over  a 


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94       Report  of  Committee  on  Reinforced  Concrete. 


^A//    <300 

M>n9^     0 

£    ^300 

^£0LH^300 

^>f//    ^300 
^An   ^20O 


JO  J 


X  5  «  ;^ 


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307 


§    ^ 


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305\ 


30.' 


^  15   JVi   >  S> 
^  d   ^  d  ^ 


§§ 


FIO.  27. — LOAD  DEFORMATION  DIAGRAMS  FOR  UPPER  SIDE  OF  BEAMS  ATBODDLI. 


£    ^00 
^£AH^O 

%An   '^200 


§   S    <S 


a  S  g  5  g  S  § 

o    C?    C5   ^   ^    c[   c> 

FIG.  28. — LOAD  DEFORMATION  DIAGRAMS  FOR  UNDER  SIDE  OF  GIRDERS  AT  END. 


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Repobt  of  Committee  on  Reinforced  Concrete. 


96 


Abne^    0, 


FIG.  29. — ^LOAD  DEFORMATION  DIAGRAMS  FOR  UPPER  SIDE  AND  UNDER  SIDE  OF 

GIRDERS  AT  MIDDLE. 


aoo 


^A// 


A//    voo 
Uorm         0 


£    ^300 
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^A/l    ^00 

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/k*/S 


I  S  * 


FIG.30. — LOAD  DEFORMATION  DIAGRAMS  FOR  CONCRETE  ON  UNDER  SIDE  OF  SLAB. 


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96        Report  of  Committee  on  Reinforced  Concrete. 


TaBLB  IV. — SCHBDULE  OF  LOADING  OPERATIONS  IN  TuRNBR-CaRTBB 

Building  Test 
Loading  Schedule, 


Day. 


Sunday. . . . 
Monday... 
TuMday... 
Wednesday 

ThUTBday.., 


Date. 


9-10-11 


0-11-11 


9-12-11 


9-13-11 


9-14-11 


Obeervationa. 


Load, 
lb.  per 
sq.ft. 


100 


200 


300 


Hours. 


lb.  per 
sq.ft. 


12  m 

to 

2  p.  M. 

7.20 

to 

12  m. 

e.30 

to 

8.16  A.  M. 

6.20 

to 

8.20  A.  M. 


100 


200 


300 


8.00 

to 

8.30  A.  M. 


I 


ling. 

ObservaUons. 

Load, 

Hours. 

lb.  per 
sq.  ft. 

Hours. 

1.30 

100 

6.10 

to 

to 

6.00  p.  M. 

8.00  p.  M. 

10.30  A.  M. 

200 

3.10 

to 

to 

3.00  p.  M. 

6.30  p.  M. 

9.00  A.  M. 

300 

3.60 

to 

800 

to 

3.30  p.  M. 

6.80  p.  M. 

1030 

to 

11.30  p.m. 

300 

3.00 

to 

3.30  p.  M. 

Unloading  Schedule, 


Friday 

Saturday. . 
Monday... 


Tuesday. 


9-15-11 


9-16-11 


9-18-11 


9-19-11 


Wednesday. 


300 


7.30         300  on  D.         3.30 

to  E,  F,  H,  to 

I  9.30  A.  M.      and  /.       7.30  p.  m. 


300  on  D.        7.20 
if,  F.  H,  to 

and  J.       9.15  a.  m. 


300  on  £ 
andff. 


9-20-11    300  on  ^ 
I     only. 


6.15  a.m. 

to 
9.20  A.  M. 


8.30  A.  M. 

Zero. 

to 

12.30  p.  M. 

300  on  £         9.30 
and  H.  to 

I  11.45  a.m. 

300  on  ^     9.30  a.  m. 
only.  to 

*    12.00  m. 


1.00 

to 

3.40  p.  M. 


300  on  Z), 

E,  P,  H, 

and  I. 

300  on  £ 
andff. 


3O0onE 
only. 


300  on  £ 
only.     I 


Zero  on 
all  bays. 


8.00 

to 

8.30  p.  M. 

6.30 

to 

8.00  p.  M. 

12.16 

to 

1.60  p.  M. 

4.16 

to 

8.00  p.  M. 

4.60 

to 

6.60  p.  M. 

4.00 

to 

6.40  p.  M. 


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Report  of  Committee  on  Reinforced  Concrete.       97 

period  of  48  hoxirs.     A  similar  method  was  used  in  the  process  of 
removing  the  load. 

Table  IV  shows  the  loading  schedule.  The  load  was  applied 
in  increments  of  100  lb.  per  sq.  ft.  based  upon  the  whole  test  area. 
The  application  of  the  load  consumed  three  days.  The  full  load 
was  left  on  48  hours.  The  unloading  schedule  is  also  shown  in 
Table  IV.  In  the  unloading,  the  load  on  panels  B  and  C  were 
first  removed,  then  the  load  on  panels  Z),  F,  and  7,  followed  by  the 


\300 


\200 

voo 


1-4// 


Nbne         O 


FIG.  31 


-LOAD  DEFORMATION  DIAGRAMS  FOR  CONCRETE  ON  UPPER  SIDE  OF  SLAB. 


removal  of  the  load  on  panel  H,  Fig.  21  is  a  view  at  a  load  of 
300  lb.  per  sq.  ft.  over  the  test  area.  The  total  load  was  over 
500,000  lb. 

Personnel  of  Testing  Staff. — ^All  instrument  readings  were 
made  by  W.  A.  Slater  and  H.  F.  Moore,  of  the  stafif  of  the  Engi- 
neering Experiment  Station  of  the  University  of  Illinois.  Mr. 
Slater  had  immediate  charge  of  the  test  as  a  whole.  A.  N.  Talbot 
was  present  during  the  work  of  preparing  for  the  test.  Three 
others  assisted  in  the  work  of  recording  and  reducing  data. 


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98       Repokt  op  Committee  on  Reinforced  Concrete. 


Table  V.— Strbss  Indications  in  Turner-Cartbh  Building  Test. 


Member. 

Gauge  Line. 

220 
244 
304 
318 
310 

202 
206 
230 
234 
236 
238 
240 
222 
224 
214 

Reinforcement. 

Gauge  Line. 

269 
311 

265 
267 
281 
293 
301 
305 
313 
315 

Concrete. 

End  of  girder 

Middle  of  girder 

Rnd  of  beam 

'siooo 

9,000 
8,000 
8,000 
4,000 

"7]666 

11,000 
9,000 
8,000 
8,000 

11,000 

5,000 

5,000 

5,000 

—3,000 

900 
Little 

'  1,166 

1,100 

1,000 

800 

u 

It 

It 

Middle  of  beam 

350 

it 

350 

ft 

200 

it 

300 

li 

tt 

It 

Rent  up  bar  in  girder 

Bent  UD  bar  in  beani 

Table  VI. — Maximum  Stresses  and  Moment  Coefficients 
in  Turner-Carter  Building  Test. 


Member. 


Girder,  End — 
"  End.... 
"  Middle . 
"      Middle. 


Intermediate  Beam,  End — 
End.... 
Middle. 
Middle. 


Column  Beam,  End. . . . 
End.... 
Middle. 
Middle. 


Reinforcement. 


Btreea. 


31,000 

ik'ySdo 

8,000 

Sl,500 

8,000 

18,600 

11,000 

lOfiOO 


17,000 
10,000 


Coefficient- 


1/lB 

1/12 
0.05 

1/12 
0.03 
1/12 
0.05 

1/12 

1/12 
0.05 


Concrete. 


Stress.       Coefficient. 


IfiOO 
900 

too 

Little 

1^00 

1,100 

S80 

350 

1,200 
950 
S50 
225 


1/12 
0.06 
1/12 


1/12 
0.07 
1/12 
0.077 

1/12 
0.064 
1/12 
0.054 


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Report  of  Committee  on  Reinforced  Concrete. 


99 


Deformations  and  Stresses. — The  results  of  observations  on 
various  gauge  lines  for  the  beams  and  girders  are  plotted  in  Figs. 
22  to  29.  Fig.  30  gives  the  deformations  in  the  concrete  on  the 
under  side  of  the  floor  slab  and  Fig.  31  those  on  the  upper  side 
Fig.  32  records  measurements  made  on  the  bent-up  bars  and 
stirrups. 

As  already  stated,  the  location  of  the  gauge  lines  is  shown  on 
Figs.  17  and  18,  the  odd  numbers  referring  to  measurement  on  the 


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no.    32. — ^LOAO    DEFORMATION  DIAQRAMS  FOR    BENT-UP    BARS    AND  BTIRRUPe. 

concrete,  the  even  numbers  to  measurement  on  the  reinforcement. 
The  numbers  in  the  two  hundreds  are  gauge  lines  on  the  under 
side  or  second  story  side,  and  the  numbers  in  the  three  hundreds 
are  on  the  upper  side  or  third  story  side. 

Stresses  and  bending  moment  coefficients  are  tabulated  in 
Tables  V  and  VI. 

The  suggestions  given  for  caution  and  care  in  interpreting 
measurements  should  be  applied  to  this  test. 


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Beams. — For  the  tensile  stresses  in  the  reinforcement  at  the 
middle  of  the  intermediate  beams  at  the  full  load  of  300  lb.  per 
sq.  ft.,  the  highest  stress  observed  ^as  11,000  lb.  per  sq.  in.  and 
the  average  stress  recorded  may  be  said  to  be  8,500  lb.  per  sq.  in. 
At  the  ends  of  the  intermediate  beams,  the  highest  stress  observed 
in  the  reinforcement  was  8,000  lb.  per  sq.  in.,  and  the  general 
value  may  be  said  to  be  7,500  lb.  per  sq.  in.  Using  the  assump- 
tions for  resisting  moment  ordinarily  taken  in  design  calculations, 
these  stresses  may  be  considered  to  correspond  to  a  bending 


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no.   33. — ^DIAGRAM  SHOWING  DISTRIBUTION  OF  COMPRESSIVE  DEFORMATION  IN 
BOTTOM  OF  COLUMN  BEAM. 

moment  coefficient  of  .05  Wl  for  the  maximum  stress  at  the  middle 
of  the  beam  and  .03  Wl  for  the  maximum  stress  at  the  end  of  the 
beam,  if  the  tensile  strength  of  the  concrete  be  not  considered. 
Assuming  a  modulus  of  elasticity  for  the  concrete  of  2,500,000 
lb.  per  sq.  in.,  the  concrete  on  the  compression  side  of  the  beams 
at  the  middle  showed  a  compressive  stress  of  350  lb.  per  sq.  in. 
and  at  the  end  of  the  beam  1,100  lb.  per  sq.  in.  It  is  apparent 
that  the  total  compressive  stress  in  the  concrete  is  greater  than 
the  total  tensile  stress  in  the  reinforcement  of  the  beams.  A 
possible  explanation  is  that  end  thrust  exists,  involving  so-called 


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Report  op  Committee  on  Reinforced  Concrete.     101 

arch  action  in  the  beams  and  floor  structure,  and  that  the  tensile 
stress  is  relieved  by  the  presence  of  this  thrust.  The  tensile 
strength  of  the  concrete  must  have  a  large  effect  on  the  resisting 
moment.  The  coefficient  of  Wl  in  the  bending  moment,  necessary 
to  give  a  compressive  stress  equal  to  the  maximum  measiu^  in 
the  concrete,  on  the  assumptions  made,  is  .077  for  the  middle  of 
the  beam  and  .07  for  the  end  of  the  b^am.  These  coeflScienta 
are  lower  than  the  value  1/12  usually  assumed  in  design  of  such 
beams. 

Girders, — For  the  tensile  stresses  at  the  middle  of  the  girders 
the  observations  showed  about  8,000  lb.  per  sq.  in.  in  the  reinforce- 


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FIG     34. — DIAGRAM  SHOWING  DISTRIBUTIGN  OF  COMPRESSIVE  DEFORMATION  IN 
INTERMEDIATE  BEAM. 

ment  at  the  middle.  This  corresponds  to  a  bending  moment 
coefficient  of  .05,  again  neglecting  the  tensile  strength  of  the  con- 
crete. The  reinforcement  at  the  end  of  the  girder  was  inaccessible. 
Assuming  a  modulus  of  elasticity  of  2,500,000  lb.  per  sq.  in., 
the  concrete  on  the  compressive  side  of  the  beam  at  the  support 
showed  a  compressive  stress  of  900  lb.  per  sq.  in.  The  reading 
at  the  middle  of  the  beam  showed  very  little  compression.  Assum- 
ing that  the  loads  on  the  girder  are  concentrated  at  the  points 
where  the  intermediate  beams  are  connected,  and  making  the  same 
assumption  of  distribution  of  stress  as  before,  the  coefficient  of 
bending  moment  was  .06.  It  seems  probable  that  the  compres- 
sion at  the  middle  of  the  span  must  be  distributed  over  a  consid- 


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102     Report  op  Committee  on  Reinforced  Concrete. 

erable  width  of  floor,  or  larger  readings  of  compression  would  have 
been  obtained. 

Decrease  in  Compression  with  Distance  from  Support. — ^In  four 
beams  measurements  of  compressive  deformations  were  taken  at 
a  series  of  gauge  lines  from  the  support  to  a  location  near  the  point 
of  inflection.  The  position  of  these  points  is  shown  in  Pig.  17. 
The  gauge  lines  No.  223,  225,  227,  229,  231,  and  233  are  on  one 
side  of  column  No.  6,  and  281,  283,  285,  287,  289,  and  291  are  on 
the  other  side  of  colxmin  No.  6.  It  may  be  expected  that  there 
will  be  full  restraint  for  the  end  of  the  beams.  Gauge  lines  243, 
241,  239,  237,  and  235  are  on  one  side  of  a  girder  and  293,  295, 
297,  299,  and  1201  are  on  the  other  side.  The  unit-deformations 
for  these  gauge  lines  at  loads  of  200  lb.  per  sq.  ft.  and  300  lb.  per 
sq.  ft.  are  plotted  in  Figs.  33  and  34. 

The  measurements  recorded  for  the  column  beams  show  con- 
siderably more  compressive  stress  than  do  those  for  the  intermediate 
beams,  perhaps  one-third  more.  This  difference  in  stress  may  be 
due  partly  to  the  deflection  of  the  girder,  and  to  the  deflection  of 
the  intermediate  beam  between  its  support  and  a  point  opposite 
the  end  of  the  column  beam,  which  would  permit  a  larger  part 
of  the  load  to  be  carried  by  the  column  beam.  It  may  be  due 
somewhat  to  the  fact  that  reinforcing  bars  are  bent  down  from  a 
point  at  the  end  of  the  column  beam,  while  in  the  intermediate 
beams  the  bars  run  horizontally  for  a  foot  from  the  face  of  the 
girder. 

The  direction  of  the  lines  in  Fig.  33  and  Fig.  34  indicates  a 
zero  stress  at  about  45  in.  from  the  face  of  column  in  the  column 
beams  and  at  about  50  in.  from  the  face  of  the  girder  in  the  inter- 
mediate beams.  In  both  cases  the  results  locate  the  point  of 
inflection  at  about  0.22  of  the  clear  span. 

T'Beam  Action. — The  distribution  of  compressive  stresses 
in  the  T-beam  formed  by  a  beam  and  the  floor  slab  (which  involves 
the  distances  away  from  the  beam  for  which  compressive  stresses 
are  developed)  has  been  a  fruitful  source  of  discussion.  Measure- 
ments parallel  to  the  axis  of  the  beam  were  taken  on  the  upper 
surface  of  the  floor  slab  immediately  above  beams  and  at  intervals 
between  them.  These  gauge  lines  are  No.  315,  317,  319,  321,  323, 
325,  and  327  (see  Fig.  17).  The  deformations  are  shown  in  Figs. 
27  and  31.     The  amount  of  these  deformations  at  points  across  the 


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Report  of  Committee  on  Reinforced  Concrete.     103 

slab  for  loads  of  200  lb.  and  300  lb.  per  sq.  ft.  is  shown  in  Fig.  35. 
It  is  apparent  that  a  somewhat  higher  stress  existed  in  one  beam 
than  in  the  other.  Taking  this  into  consideration,  the  compres- 
sive stress  varies  quite  uniformly  from  one  beam  to  the  other,  and 
the  full  width  of  the  floor  slab  may  be  said  to  be  effective  in  taking 
compression.  The  overhang  (counting  to  the  midpoint  between 
beams)  is  6}  times  the  thickness  of  slab.  It  will  be  noticed  that 
the  conclusions  are  the  same  as  given  for  the  Wenalden  building 
test. 

Readings  were  also  taken  on  the  under  side  of  the  floor  slabs 
parallel  to  the  beams  at  three  places  (No.  1205,  1211,  and  1213), 
but  the  conditions  attending  the  location  of  these  points  do  not 
permit  conclusions  to  be  drawn. 

Floor  Slab. — Measurements  were  taken  on  the  floor  slab  in 


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no.    35. — DIAQBAM  SHOWING    DISTRIBUTION    OF    COMPRESSIVE    DEFORMATION 
ACROSS  FLANGE   OF  TEE  BEAMS. 

the  direction  of  its  span  at  three  places  on  the  under  side  and  at 
one  place  on  the  upper  side  immediately  above  one  of  the  lower 
measurements.  These  gauge  lines  were  Na  277  on  the  under  side 
of  the  slab  close  to  a  girder  (Fig.  17),  No.  279  on  the  under  side  of 
the  slab  5  ft.  from  the  edge  of  the  girder,  No.  309  (Fig.  18)  on  the 
upper  surface  immediately  above  No.  279,  and  No.  1203  (Fig.  17) 
on  the  under  side  half  way  between  girders.  The  measurements 
are  plotted  in  Figs.  30  and  31.  As  might  be  expected  from  being 
close  to  the  girder  and  near  the  level  of  its  neutral  axis,  No.  277 
showed  little  deformation.  The  pair  of  gauge  lines  (No.  279  and 
309)  shows  less  deformation  than  would  be  calculated  by  the  ordi- 
nary beam  formula,  but  perhaps  not  less  than  would  be  the  case 
if  the  tensile  strength  of  the  concrete  is  considered  to  be  quite 
effective.     The  reading  of  No.  1203  was  even  smaller  than  279. 


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104     Report  of  Committee  on  Reinforced  Concrete. 

All  the  stresses  found  in  the  floor  slab  were  low.  The  deformations 
parallel  to  the  beams  were  discussed  under  T-beams. 

Bond  Stresses, — ^At  the  ends  of  the  beams  the  reinforcing  bars 
lapped  over  the  center  line  of  the  girder  a  distance  of  15  in.  An 
effort  was  made  to  determine  whether  there  was  a  movement  of 
one  of  these  bars  with  reference  to  the  adjoining  concrete  and  with 
reference  to  the  adjoining  bar;  also  whether  the  deformation  in 
the  stub  end  of  the  reinforcing  bar  was  the  same  as  in  the  adjoin- 
ing bar.  Fig.  36  shows  the  location  of  the  reinforcing  bars  with 
reference  to  each  other,  and  the  position  of  the  gauge  lines.  No. 
312-14  in  comparison  with  No.  312  and  314  will  indicate  any 
relative  movement  of  one  bar  with  respect  to  the  other,  and  No. 
312c  and  314c  in  comparison  with  No.  312  and  314,  respectively 
will  indicate  any  movement  of  the  bars  with  respect  to  the  con- 
crete. 

It  appears  possible  that  the  initial  reading  of  No.  314  is 


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no.    36. — ^ARRANQEMENT   OF   GAUGE    POINTS  TO  TEST  FOB  MOVEMENT   OF   BAR 
RELATFVE  TO  CONCRETE. 

slightly  in  error,  and  the  remarks  already  made  about  quantitative 
interpretation  of  results  and  the  chances  for  variations  in  stresses 
in  adjacent  bars  or  in  adjoining  concrete  should  be  borne  in  mind 
in  studying  the  results.  It  seems  evident  that  No.  314  (on  the 
lapped  bar)  records  considerable  less  stress  than  No.  312.  The 
measurements  indicate  a  possibility  that  the  right-hand  point 
of  gauge  line  No.  314  has  moved  to  the  right  relatively  to  the  right- 
hand  point  of  No.  312,  though  this  amount  may  not  be  more  than 
the  amount  of  initial  slip  necessary  to  develop  the  requisite  bond 
stress.  The  measurements  taken  have  no  bearing  on  whether 
the  left-hand  point  of  No.  314  has  moved.  The  measurements 
also  indicate  that  there  was  no  motion  of  the  left-hand  point  on 
the  reinforcing  bar  (No.  312  gauge  line)  relatively  to  the  concrete 
at  its  side,  though  it  must  be  borne  in  mind  that  the  point  taken 
was  so  close  to  the  bar  that  only  slip  and  not  distortion  of  concrete 
could  be  measured. 


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Report  of  Committee  on  Reinforced  Concrete.     105 

Web  Deformations, — No  diagonal  tension  cracks  were  visible 
on  any  of  the  beams  or  girders. 

In  girder  4  measurements  were  taken  on  the  diagonal  portion 
of  a  reinforcing  bar,  one  of  the  bars  which  is  provided  to  take 
negative  bending  moment.  This  is  shown  in  Fig.  17,  Section  K-K. 
The  gauge  lines  are  No.  222,  224,  and  226  The  position  of  the 
gauge  lines  is  also  shown  in  Fig.  16.  The  measurements  are  plotted 
in  Fig.  32.  It  was  impracticable  to  measure  the  deformation  at 
a  point  closer  to  the  support.  The  measurements  show  about 
the  same  stress  at  No.  222  and  224,  perhaps  5,000  lb.  per  sq.  in. 
The  stress  at  No.  226  is  materially  less.  It  is  not  improbable 
that  there  was  tension  in  this  rod  throughout  its  length.  As  there 
was  considerable  compression  measured  in  the  gauge  lines  on  the 
bottom  of  the  girder  below  No.  222,  it  seems  probable  that  a 
crack  was  formed  in  the  top  of  the  floor  slab  somewhere  above  No. 
222,  but  as  this  space  was  filled  in  with  bags  of  cement  no  observa- 
tion was  made  during  the  test,  and  inspection  of  this  space  after 
the  load  was  removed  seems  to  have  been  overlooked.  At  the 
other  end  of  the  girder,  near  column  6,  a  fine  test  crack  was  found 
on  the  upper  surface  of  the  floor  2  in.  from  the  face  of  the  column 
extending  across  the  width  of  the  girder  and  beyond.  This 
extended  through  the  floor.  A  similar  crack  was  observed  on 
girder  3  near  column  15. 

Gauge  line  No.  228  is  on  a  stirrup  (see  Fig.  16).  This  stirrup 
is  in  an  inclined  position.  It  is  not  known  what  bar  it  is  intended 
to  be  connected  with,  nor  whether  there. is  connection  with  a 
tension  bar.  The  gauge  line  is  in  a  region  of  the  beam  where  hori- 
zontal compressive  stresses  may  be  expected.  The  measurement 
in  the  stirrup  at  the  first  increment  of  load  shows  tension  (see  Fig. 
32)  and  subsequent  increments  give  compression.  It  should  be 
noted  that  readings  could  not  be  taken  on  the  upper  end  of  the 
stirrup.  If  the  upper  ends  are  merely  bent  out  into  the  floor  slab 
it  is  hard  to  see  that  the  stirrup  may  be  expected  to  be  useful  in 
transmitting  web  stresses. 

In  beam  9  (see  Fig.  17,  Section  L-L,  gauge  line  No.  218) 
measurement  was  taken  on  the  diagonal  portion  of  a  reinforcing 
bar  which  is  carried  through  the  girder  at  its  top  and  a  few  inches 
beyond.  See  also  Fig.  16.  This  shows  a  tension  of  3,000  to  5,000 
lb.  per  sq.  in.     (See  Fig.  32.)     This  bar  was  inaccessible  from  the 


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FIG.— 37.   LOAD  DEFLECTION  DIAGRAMS. 


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Report  op  Committee  on  Reinforced  Concrete.     107 

top  of  the  floor,  but  the  gauge  lines  on  the  companion  bar  (No. 
324  and  318)  show  about  5,000  and  9,000  lb.  per  sq.  in.  Measure- 
ments in  the  diagonal  portion  of  a  single-bend  bar  (gauge  lines 
No.  216  and  214,  Fig.  17)  which  extends  only  to  the  center  of  the 
supporting  girder  indicate  a  small  compression  in  the  bar  (see 
Fig.  32).  A  stirrup,  which  like  the  one  in  the  girder  was  close  to 
the  end  of  the  beam  and  was  inclined  so  that  its  lower  end  was 
nearer  the  support  than  its  upper,  showed  shortening  of  the  stir- 
rup (see  gauge  line  No.  212,  Figs.  16, 17,  and  32).    In  both  cases, 


FIQ,  38. — CABINET  PROJECTION  SHOWING  BEAMS  AND  GIRDERS  AND  POSITION  OF 

TEST  CRACKS. 

the  arrangement  was  such  that  the  stirrup  could  hardly  be  effec- 
tive. 

The  amount  of  the  vertical  shear  in  the  beams  and  girders 
was  such  that  diagonal  tension  cracks  might  be  expected  except 
for  the  small  tensile  stresses  in  the  top  of  the  girder  and  the  end 
constraint  which  seems  to  have  been  developed  in  both  beams  and 
girders. 

Deflections. — ^The  deflections  of  the  beams  (including  that  due 
to  deflection  of  girder)  and  the  deflections  of  girders  are  given  in 
Fig.  37.     The  location  of  the  deflection  points  is  shown  in  Fig.  19. 


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108     Report  of  Committee  on  Reinforced  Concrete. 

The  effect  of  time  upon  the  deflection  is  shown  by  the  increase 
in  deflection  under  constant  load.  The  change  when  portions 
of  the  load  had  been  removed  may  be  due  in  part  to  the  time 
element  and  in  part  to  the  effect  of  location  of  the  load  on  the 
panels.  The  deflections  seem  relatively  small,  especially  when 
compared  with  deflections  obtained  in  laboratory  tests  of  beams 
carrying  the  same  loads.  The  effect  of  the  time  element  is  indi- 
cated on  these  diagrams.  The  conditions  were  such  that  the  sup- 
ports were  subject  to  possible  displacement  by  workmen. 

Columns. — Readings  were  taken  on  the  four  faces  of  Column 
No.  6  just  below  the  girders,  but  the  results  are  not  consistent 
enough  to  warrant  attempting  drawing  conclusions. 

Test  Cracks. — Fine  tension  cracks  were  observed  in  the  lower 
part  of  the  beams  and  girders.  The  location  of  the  observed 
cracks  is  shown  on  Fig.  38.  The  appearance  of  these  fine  cracks 
is  similar  to  those  observed  in  laboratory  tests.  They  would 
not  be  noticed  without  specially  careful  examination. 

The  floor  cracks  already  mentioned  indicate  the  development 
of  the  tensile  stresses  in  the  beams  and  girders  at  the  support. 

The  limitation  of  space  and  time  have  prevented  the  pre- 
sentation of  other  matters  which  were  observed  in  the  tests. 
For  example,  the  observations  on  deformations  during  the  48 
hours  time  with  the  full  loading  showed  in  general  a  slight  increase 
in  the  deformations  in  the  reinforcement  and  in  the  concrete. 
It  is  hoped  to  take  up  some  of  these  matters  at  another  time. 
It  was  not  possible  to  give  full  attention  to  every  feature  upon 
which  information  was  sought,  and  in  some  cases  isolated  points 
were  used  with  a  view  of  determining  tendencies,  and  in  these 
naturally  there  is  less  certainty  in  the  indications. 

Part  II.    Test  of  a  New  Type  of  Flat  Slab  Floor 
Construction. 

Building. — The  Powers  Building,  Fig.  39,  is  a  three  story 
and  basement  warehouse  located  at  Minneapolis,  Minn.  The 
exterior  walls  of  the  building  are  bearing  walls  and  there  is  one 
row  of  columns  through  the  middle  of  the  building.  The  floors 
are  flat  slabs,  reinforced  in  two  directions  with  high  elastic  limit 
deformed  bars.     Fig.  40  shows  a  basement  and  first  floor  plan 


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Report  op  Committee  on  Reinforced  Concrete.      109 

of  the  building,  Fig.  41  the  reinforcement  in  the  floor  tested  and 
Fig.  42  the  reinforcement  in  place. 

General  Outline  of  Test — ^The  first  floor  of  the  building  was 
selected  for  the  test  by  the  Building  Inspector  of  the  City  of 
Minneapolis,  as  this  represented  an  acceptance  test  for  the  new 


FIG.   39. — POWERS   BUILDING,    MINNEAPOLIS,    MINN. 

design.  At  the  time  of  the  test  the  floor  was  about  3  months  old. 
Four  panels  were  loaded  to  200  lb.  per  sq.  ft.  (the  design  load) 
and  then  two  panels  were  loaded  to  twice  this  amount.  Cement 
in  bags  was  used  for  the  load,  piled  in  piers  to  prevent  arching. 
The  load  was  arranged  as  shown  in  Fig.  44  until  the  design  load 
was  reached,  while  for  the  maximum  load  Panels  2  and  3  only 


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no     Report  of  Cobimittee  on  Reinforced  Concrete 


50 


.J^ 


«Si 


open^ 


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ytasement  Columns  •  Zo'square       % 


first  ^ory  Columns-  id'square. 


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Rectangles  over  Columns 
which  are  iwo  inches 
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Report  of  Committee  on  Reinforced  Concrete.      Ill 


dors  extend  ^  same  dirsction  as  lettering  indicating  them  ■  straight  A  bent 
bars  alernate.  -  StmigHt  bars  extend  6' past  margin  of  panel  ana  bent  bars 
extend  to  quarier-jpoinr  ofadjdcenf  panel 

There  one  onfy  ho  layers  of  bars  m  the  top  of  the  siaband  two  ^ 
vss\  lowers  in  the  bottom.  The  bent  bars  extending  across  the  building  fbrm% 
^  the  bottom  tiyer  in  the  middle  oftfjepanel  and  the  top  layer  over  the 


the  pat 
Mm 


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TIQ.  41. — DIAGRAM  8H0WINQ   ARRANGEMENT  OF  REINFORCEMENT. 


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112     Report  of  Committee  on  Reinforced  Concrete. 

were  loaded.  The  wide  aisles  shown  were  necessary  for  the 
accommodation  of  the  mstruments  and  observers.  All  tabulated 
loads  per  square  foot  and  the  loads  used  in  plotting  are  in  every 
case  the  total  load  on  the  panel  divided  by  the  area  of  the  panel; 
the  intensity  of  the  load  under  the  piers,  of  course,  is  greater. 
Deflections  of  the  various  panels  were  measured  under  different 
stages  of  loading  and  also  the  deformation  of  the  reinforcement 
and  concrete  due  to  these  loads. 


FIG.    42. — REINFORCEMENT  IN   PLACE,    POWERS  BUILDING. 

Instruments. — The  deflections  were  measured  with  a  deflec- 
tometer,  see  Fig.  1. 

Deformations  in  the  reinforcement  and  concrete  were  meas- 
ured with  an  8-in.  Berry  strain  gauge.  Fig.  43,  which  reads  direct 
to  1/2000  of  an  inch,  or  by  estimation  to  one-fourth  of  this 
amount.  As  slight  variation  is  possible,  5  readings  were  taken 
at  each  point  and  the  average  of  these  assumed  to  be  correct. 
Readings  were  taken  at  intervals  throughout  the  test  on  stand- 
ard bars  and  on  standard  points  placed  in  imstressed  portions  of 
the  concrete;  the  temperature  corrections  so  observed  have  been 


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Report  of  Committee  on  Reinforced  Concrete.      113 

made  to  the  readings.  There  are  many  diflSculties  mvolved  in 
measuring  deformations  under  conditions  such  as  exist  in  a  test 
of  this  kind.     In  view  of  these  difficulties  extreme  accuracy  can- 


Frame 


'Ame6  Gauge 


1 1 

■Plunger  I 

ii 


Lever 


Hxed  Leg 


^35  Hole 


^55  Hole 


no.  43. — BEBBT  STRAIN  QAUOE. 

not  be  hoped  for,  but  serviceable  results  can  be  obtained  by  a 
trained  observer.  Observations  were  made  by  W.  A.  Slater, 
University  of  Illinois,  and  F.  J.  Trelease  of  the  Research  Depart- 
ment, Corrugated  Bar  Company. 


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114     Report  of  Committee  on  Reinforced  Concrete. 


FIG.   44. — ARRANGEMENT  OF  LOADING. 


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Report  of  Committee  on  Reinforced  Concrete.       115 

Application  of  Load, — ^The  test  continued  for  9  days,  July  27 
to  August  4,  inclusive,  1911.     The  loading  was  in  10  stages  as 

Table  VII. — Schedule  of  Loading  Operations. 


Stage. 

Load  ic 

Place 

Loadio 

Poiinds 

per  Panel  and  per  Square 
Foot. 

From 

To 

Panel  1. 

Panel  2. 

Panel  3. 

Panel  4. 

1 
2 
3 

4 
5 
6 

1.45  P.M.,  7-27 
11.10  A.M.,  7-27 
4.45  P.M.,  7-28 
10.45  A.M..  7-29 
3.40  P.M..  7-29 
7.00  P.M..  7-29 
3.15  P.M..  8-1 
8.20  a.m.,  8-2 
4.30  P.M..  8-2 
10.35  a.m..  8-3 

8.40  A.M.,  7-28 
2.00  P.M..  7-28 
8.45  A.M.,  7-29 
1.25  P.M..  7-29 
5.40  P.M..  7-29 
11.00  a.m..  7-31 
4.25  P.M..  8-1 
9.15  a.m..  8-2 
7.15  A.M..  8-3 
3.45  P.M..  8-3 

13,300 
33.440 
53,200 
34.200 
15,200 

52 
132 
210 
135 

60 

13.300      51 
33,440    128 
53.200    204 
72,200    276 
91.200  1  350 
106,400i  408 

L^.iiLtO 
3^S.].|.0 
f.:j,JiiO 

r-'.-iiO 

ItKLiOO 
lOf-MK) 

Sa.Ui'O 

51 
129 
206 
280 
354 
414 
198 

13,300 
33.440 
53,200 
34,200 
15.200 

51 
128 
204 
131 

58 

7 

96,900  1  370 
106.780'  408 

8 

9 

53,010 
21.660 

202 
83 

10 



Note.— Started  placing  Stage  1  at  10  A.  M..  7-27-1911.     All  load  removed  at  4.20  P.  M.. 
8-3-1911. 

will  be  noted  from  Table  VII,  which  shows  the  arrangement  of  the 
load  at  various  stages  and  the  length  of  time  each  load  remained  on 


FIG.  46. — DESIGN  LOAD  IN  PLACE  ON  FOUR  PANELS. 

the  floor.     Readings  were  first  taken  on  all  points  with  the  floor 
unloaded  and  then  a  load  approximately   equivalent  to  50  lb. 


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116     Report  of  Committee  on  Reinforced  Concrete. 


■X 


•7 


•  6 


•5 


•4 


•  J 


•  2 


'^  r 

I 


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!   L 


I I 


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•  26 

•  25 

•24        •3? 

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•21  ^29 
•20       ^28 

•  19 


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FIG.  46. — ^LOCATZON  OF  DEFLECTION  POINTS. 


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Report  op  CoMBniTEE  on  Reinforced  Concrete.      117 

per  sq.  ft.  was  applied  over  4  panels,  Fig.  44.  Another  set  of 
readings  was  taken  and  the  load  increased  to  125  lb.  per  sq.  ft. 
This  method  of  alternate  loading  and  reading  obtained  through- 
out the  test.  When  the  desigp  load  of  200  lb.  was  reached,  how- 
ever, the  load  on  Panels  1  and  4  was  moved  by  stages  to  Panels 
2  and  3,  so  that  finally  Panels  1  and  4  were  completely  unloaded 
and  Panels  2  and  3  were  loaded  to  about  400  lb.  per  sq.  ft.     The 


Table  VIII. — Deflections  in 

Inches. 

Set 

1 

2 

3 

4 

6 

6        7    1    8    '    9 

10   1    11 

12 

13 

14 

15 

16 

Load 

DL 

1 

1 

2 

3 

3        4        5    1    6 

6    1    6 

7 

9 

9 

10 

DL 

^ 

0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 

-.005 
.005 
.014 
.004 
.000 
-.002 
-.001 
-.016 
.004 
.038 
.000 
.001 
-.001 
.008 
.016 
.017 
.012 
.010 
.013 
.022 
.021 
.020 
.028 
.019 
.016 
.008 
-.001 
.014 
.013 
.015 
.017 
.018 

.000 
.015 
.026 
.034 
.005 
.010 
.007 
-.003 
.012 
.043 
.000 
.002 
.012 
.022 
.019 
.028 
.023 
.019 
.028 
.035 
.033 
.037 
.038 
.041 
.027 
.021 
.006 
.023 
.022 
.018 
.029 
.031 

.004 
.032 
.057 
.055 
.003 
.012 
.008 
.000 
.017 
.039 
.006 
.005 
.015 
.051 
.054 
.067 
.060 
.049 
.068 
.085 
.081 
.079 
.090 
.106 
.069 

!oio 

.061 
.169 
.065 
.079 
.078 

.Oil 
.052 
.079 
.066 
.008 
.010 
.003 
.009 
.019 
.046 
.014 
.009 
.013 
.111 
.126 
.142 
.133 
.118 
.137 
.205 
.213 
.224 
.236 
.249 
.154 
.321 
.021 
.158 
.176 
.179 
.196 
.196 

'      ;      ' 
;     ,     1 

.016'  .026'  .043    .065 
.060    .091    .143,   .197 
.090    .139,  .217    .294 
.073,   .102    .144    .195 
.013,  .0171  .035'   .050 
.008    .010    .015    .020 
.003    .005,   .0061   .009 
.0121   .007    .002:-. 002 
.021:   .028    .037,   .046 
.056,   .067'   .076    .101 
.014,  .020'  .033'  .035 
.009,  .011]  .009'  .008 
.013'  .013,   .0151   .015 
.126    .134,   .1631   .152 
.146'   .163'   .182.   .209 
.155    .175'   .220;   .242 
.149;   .163'   .190'   .198 
.138    .141    .144'   .137 
.1681  .1631   .1451   .136 
.238    .251,  .2731  .283 
.255,   .278    .320|   .348 
.264'   .294'   .346,   .374 
.278    .303'  .326    .363 
.2861  .289    .318'  .316 
.156    .179    .1661   .148 

.341!   .326,   .3061 

.0291   .034    .027,   .023 
.1841  .196|  .2061  .229 
.211,   .2301   .2661   .291 
.214    .234    .273    .305 
.228'   .248    .285    .309 
.229,   .236    .256    .268 

.082 
.237 
.351 
.243 
.063 
.028 
.014 
.000 
055 

.07. 

•:«4 

.070 


.059 
.174 
.271 
.196 
.070 
.026 

.040 
.112 
.159 
.102 
.047 
.012 
.010 
-.003 
.031 
.070 
.023 
.006 
.011 
.120 
.194 
.210 
.177 
.136 
.130 
.272 
.327 
.350 
.350 
.313 
.149 

.040 
.110 
.159 
.108 
.050 
.016 

-!6d6 
.030 
.066 
.030 
.007 

".lis 

.187 
.207 
.169 
.130 
.131 
.260 
.308 
.333 
.312 
.304 
.151 

.042 
.114 
.161 
.113 
.048 
.016 
.014 
.003 
.026 
.059 
.026 
.007 
.015 
.095 
.156 
.171 
.141 
.110 
.120 
.226 
.265 
.284 
.286 
.269 
.130 

'!i55 

.OOi 

-.002 

10 
11 

.112 
.049 
.009 
.022 
.135 
.216 
.240 
.205 
.147 
.132 
.307 
.378 
.413 
.401 
.349 
.148 
.137 
.027 
.243 
.319 
.341 
.342 
,287 

.120 

.104 

.056 

12 
13 

.010 

.008 

.009 

14 

15 

16 

.131 

17 

18 

19 
20 
21 

.148 

.161 
.320 

.282 

22 
23 

.421 

.424 

.214 

24 
26 
26 

'!i49 

.363 
.156 

"iw 

27 

.022 
.214 
.287 
.299 
.302 
.270 

";266 
.268 
.284 
.290 
.261 

.021 
.179 
.242 
.254 
.255 
.230 

28 
29 

30 

81 

82 

load  was  next  removed  from  Panel  3  and  finally  from  Panel  2, 
readings  being  taken  at  intervals  during  the  unloading.  Fig.  45 
shows  the  design  load  in  place  on  the  four  panels. 

Data. — ^Deflection  readings  were  taken  at  32  points.  Fig.  46. 
The  deflections  are  given  in  Table  VIII  and  are  plotted  in  Figs. 
47  and  48.  The  load  plotted  in  these  figures  and  in  the  stress 
curves  is  the  load  per  square  foot  on  the  central  panels.  The 
stage  of  loading  can  be  obtained  by  referring  to  Table  VIII. 


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118     Report  of  Committee  on  Reinforced  Concrete. 


6     aJ    ai     o     37    oB    aS    o     ST    a?    53" 
Deflection  In  Inches 


FIG.   47. — DEFLECTION  CUBVK8. 


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Report  of  Committee  on  Reinforced  Concrete.      119 

Deformation  of  the  reinforcement  was  read  at  30  points  and 
of  the  concrete  at  31  points.  The  location  of  these  points  is 
shown  in  Figs.  49  and  50.  Table  IX  gives  the  embedment  to 
center  of  bar;  thickness  of  the  slab  and  finish  coat;  net  thickness 


^ 


Loaded  Portion 


^;^Me■»>qJ>vlM>«LWA^a^J;Jft^;.w;^■l!<^aw■i^^^^^^^^^ 


% 


FIG.   48. — SECTIONS  OF  FLOOR  SHOWING  DEFLECTIONS. 

of  the  rough  concrete  slab,  deducting  the  thickness  of  the  finish 
coat  from  the  total  thickness  of  slab,  as  the  finish  coat  was  found 
to  be  loose  in  many  places  and  did  not  have  much  load-carrying 
capacity;  and  also  the  effective  depth  of  the  reinforcement  on 
which  the  strain  was  measured. 


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120     Rbfobt  of  Comhtttee  on  Reinfobcisd  CoNCBinv. 


o4« 


my 


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•-•  Indicates  Points  on  Top  of  5lab 

o-o  Indicates  Points  on  bottom  of  5lab 

no.  40. — LOCATION  OF  DEFORMATION  GAUGS  POINTS  OR  REINFORCEMENT. 


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Report  of  Committee  on  Reinforced  Concrete.      121 




^ 

1 —     " 

' 

f" 

IT 

• 

— 

_L_. 

! 
1 

i 

1 

I — 
1 

m  "^   ''^ 

1 

1 
1 

H 

L. 

4<»> 

r^ 

I     1 

[" 

1 

1 
1 
I 

1 

J 

r- 

415-^                      405^ 
J3/5                    .,p 

305 

*       304 
1 

All  Gauge  Lengths 

Q' 

1 

1 
I 
1 

^r 

^ 

^311                      307 

1 

r-' 

•-•  Indicates  Points  on  Top  of  J  lab 

o-o  Indicates  Points  on  dottom  of  5lab. 

nOt.    60.— LOCATION  OF  DBFORMATION  GAUGE   POINTS  ON  CONCRETE. 


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122      Report  of  CoMBniTEE  on  Reinforced  Concrete. 

The  observed  elongations  and  corresponding  unit  stresses, 
based  on  an  assumed  modulus  of  30,000,000,  in  the  reinforcement 
are  given  in  Table  X.  Unit  reinforcement  stresses  are  plotted 
against  the  load  per  square  foot  on  Panel  2  in  Figs.  51  and  62.  A 
series  of  readings  taken  by  Mr.  Slater  on  one  of  the  bars  over  the 
colunm  cap  shows  that  a  bond  stress  of  135  lb.  per  sq.  in.  under 
maximum  loading  existed  at  that  point. 

Table  IX. — Dimensions  at  Deformation  Gauge  Points. 


Embed'- 

Thickness  of 

Net  Thickness  of 
Slab,  in  in. 

Effective  Depth 
of  Bars,  in. 

Gauge    - 
Point. 

ment  of 
Bar  to 

Slab. 

Finish 

From 

From 

center,  in. 

in. 

Coat.  in. 

Actual. 

Plans. 

Actual. 

7V. 

Plans. 

101 

IVi 

9Vs 

1  V4 

7V« 

7«/4 

7»i,* 

102 

1 

OVa 

7Vi 

8V. 

8V4* 

103 

l"/if 

9Vt 

" 

7Vi 

" 

7Vi« 

7  v.* 

104 

IVm 

91. 

•  « 

7Vt 

*• 

7»»/i« 

8V4* 

105 

IVt 

8Vs 

•• 

7  V. 

" 

7V. 

7Vi» 

106 

1V4 
1  "/!• 

107 

"difii" 

;. 

"sv;."' 

;• 

'■7Vi"" 

"Viu*" 

108 

1  Vt 

109 

2Vi« 

"sifV" 

•* 

"7V." 

*• 

"6«A.'  ■ 

"7ij\i" 

111 

l»/w 

8»»/w 

•' 

7  "/!• 

•* 

7V. 

7V.« 

112 

IVw 

9 

** 

7V4 

" 

7Vw 

8V4* 

118 

1  »/!• 

0»'w 

114 

"svV" 

:. 

"7V«"* 

"  *  *  * " 

"7»/i;" 

"svii" 

115 

lu/is 

116 

IVs 

118 

1V4 

"s'^'lu" 

•• 

**7»Vii" 

" 

••7U/1'." 

"SVii" 

120 

OVw 

l>/» 

122 

"si/V" 

*"*"'"' 

■'7Vi  " 

"Vvi" 

■'s  1/4*  ' 

201 

3Vw 

lOV. 

IV4 

9V. 

"ovi'" 

7Vi« 

8». 

202 

3Vi 

lOVi 

l»/4 

9V. 

9V4 

7V4 

9 

203 

2V8 

9V. 

n/4 

7V. 

7V4 

7 

6Vi 

204 

2Vw 

11  Vi« 

l»/4 

9>*/i« 

9V4 

8V« 

9 

205 

3»/» 

10  v» 

1V4 

9  v. 

9  "A 

7V. 

8Vi 

206 

3Vi« 

10  "/w 

1  Vi 

9Vi« 

9«/« 

7Vs 

9 

207 

2Vi 

11  1/4 

1 

10  V4 

9V4 

8Vi/ 

8V« 

208 

2>/i« 

8"/m 

IVii 

7Vb 

7V4 

6Vt 

7 

200 

8  1/4 

9 

l»/4 

7V4 

7V4 

5V4 

6V« 

210 

2  Vie 

91/1. 

l»/l« 

8 

7V4 

6Vt 

7 

*  Assuming  1  \  in.  finish  coat. 

Table  XI  gives  the  observed  elongations  and  corresponding 
miit  concrete  stresses.  These  concrete  stresses  are  based  on  an 
assumed  modulus  of  2,000,000  and  are  plotted  against  loads  per 
square  foot  in  Figs.  53  and  54. 

A  summary  of  the  unit  stresses  is  given  in  Table  XII,  the 
stresses  giveii  being  the  maximum  probable  values. 

During  the  test,  cracks  were  carefully  searched  for  with  an 
electric  light  and  recorded  as  found.  Their  location  is  shown 
in  Fig.  55.     Most  of  these  cracks  were  very  minute  and  difficult 


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Report  op  Committee  on  Reinforced  Concrete.      123 


Tablb  X. — Deformations  in  Inches  and  Reinforcement  Stresses  in 

Lb.  per  Sq.  In. 


Set 

1 

2 

1 
3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

LoMl 

DL 

DL 

1 

1 

2 

3 

3 

4 

5 

6 

6 

7 

8 

9 

10 

DL 

Gauge 
Point 
101 

102 

103 

104 

105 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0.0 
1685 

0.3 
560 

-0.3 
-560 

-0.5 
-040 

0.4 
750 

•0.7 
1310 

0.8 
1600 

-0.5 
-040 

0.3 
560 

1.2 
2250 

0.8 
1500 

0.8 
1500 

0.5 
940 

0.4 
750 

0.3 
560 

-0.3 
-560 

-0.6 
-1120 

-0.7 
-1310 

-0.8 
-1600 

-0.5 
-940 

-0.2 
-380 

0.3 
560 

-0.1 
-190 

-0.3 
-560 

-0.3 
-*60 

0.1 
190 

-0.6 
-1120 

0.2 
380 

-0.5 
-940 

-0.5 
-040 

-0.9 
-1690 

-0.3 
-«60 

-0.2 
-380 

-0.3 
^60 

1.0 
1880 

1.1 
2060 

05 
940 

-0.1 
-190 

0.6 
1120 

-0.9 
-1690 

-0.4 
.750 

0.5 
040 

-0.1 
-190 

0.6 
1120 

-0.4 
-750 

0.3 
560 

-0.4 
-750 

0.1 
190 

-0.5 
-940 

0.1 
190 

-0.5 
-940 

-1.6 
-^000 

-0.4 
-760 

0.9 
1690 

-1.0 
-1880 

0.3 
560 

-0.1 
-190 

-0.2 
-380 

-0.9 
-1690 

0.5 
940 

0.2 
380 

3.3 
6200 

-0.1 
-190 

8.6 
6740 

-0.5 
-940 

0.2 
380 

0.0 

••••• 

0.7 
1310 

4.2 
7880 

0.9 
1600 

4.7 
8810 

1.1 
2060 

4.3 
8060 

2.7 
5060 

5.0 
9380 

1.6 
3000 

4.3 
8060 

2.7 
5060 

5.7 
10690 

2.0 
3750 

4.2 
7880 

3.5 
6560 

6.0 
11250 

2.2 
4120 

4.4 

8250 

4.2 
7880 

7.0 
13120 

2.4 
4600 

6.6 
10500 

4.8 
9000 

7.7 
14440 

1.9 
3560 

4.0 
7500 

3.9 
7310 

5.7 
10690 

-1.0 
-1880 

1.6 
3000 

3.0 
5620 

3.4 

6380 

4.9 
9190 

-0.3 
-560 

2.8 
5250 

2.7 
5060 

2.0 
3750 

3.7 
6040 

-1.2 

:::::  ;:::: 

-2250 

106 

1.5 
2810 

8.0 
15000 

0.6 
1120 

0.8 
1500 

107 

0.0 

0.0 

-0.5 

-940 

106 

0.3 
190 

0.2 
380 

-1.8 
-3380 

0.2 
380 

5.3 
9940 

-0.6 
-1120 

1.2 
2250 

-0.8 
-1500 

0.2 
380 

-0.6 
-1120 

2.8 
5250 

1.7 
3190 

1.5 
2810 

1.6 
3000 

7.0 
13120 

0.6 
04G 

0.3 
560 

0.9 
1690 

-2.1 
-3940 

-0.8 
-1500 

1.8 
3380 

-2.4 
-4500 

-3.1 
^10 

2.4 

4500 

-3.0 
-5600 

0.3 
560 

.20 
3750 

-2.5 
-4600 

109 
110 

2.2 
9120 

0.8 
1500 

0.8 
1500 

1.2 
2250 

111 

-0.3 
^60 

5.9 
11060 

5.6 
10500 

-1.6 

-3000 

112 
113 

••••• 

6.3 
11810 

0.4 
750 

2.1 
3940 

0.3 
560 

0.7 
1310 

-0.7 
-1310 

2.9 
5440 

5.4 
10120 

1.2 
2250 

2.7 
5060 

0.9 
1690 

1.3 
2440 

-1.4 
-2620 

1.9 
3560 

6.0 
11250 

0.3 
560 

1.5 
2810 

0.1 
190 

1.5 
2810 

-1.5 
-2810 

2.4 
4500 

6.1 
11440 

1.4 
2620 

7.6 
14250 

4.0 
7500 

114 

2.0 
3750 

1.2 
2250 

1  7 

3190 

115 

-0.1 
190 

1.7 
3190 

-0  R 

116 

1.2 
2250 

1.2 
2250 

0.8 
1500 

117 

-040 

118 

2.1 
3940 

2.7 
5060 

1.3 

2440 

120 

1  0.7 

1310 

1 

0.2 

1  380 

0.8  1.2 
1500  2250 

0.4  2.7 
750,  5060 

-0.4i  -0.1 
-750  -190 

0.5 

940 

122 
201 
202 
203 

1.5 
2810 

7.6 
14250 

-0.1 
-190 

1.4 
2620 

2.0 
3750 

8.1 
J5190 

0.1 
190 

3.0 
5620 

1.8 
3380 

9.2 
17250 

-0.8 
-1500 

3.9 
7310 

3.1 
5810 

9.1 
17060 

-0.5 
-940 

4.0 
7500 

3.7 
6940 

10.1 
18040 

-0.6 
-1120 

3.4 
6380 

3.1 
5810 

9.1 
17060 

9.5 
17810 

1.8 
3380 

2.8 
5250 

7.8 
14620 

2.1 
3940 

2.4 
4500 

5.8 
10880 

2.4 
4500 

2.5 
4690 

5.2 
9750 

-0.2 

Digitized  by 


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124     Report  op  Committee  on  Reinforced  Concrete. 


Table  X. — Continued. 


Set 

Load 

Gauge 

Point 

204 

205 

200 

207 

208 

208 


209 


210 


1 

2 
DL 

0.4 

DL 

0 

0 

750 

0 

0.1 

0 

190 

0 

0.4 

0 

750 

0 

-0.8 

0 

-1500 

-0.2 
-380 


-0.1 
-190 


0.3 
560 


0.6 
1120 


0.6 
1120, 


0.7 
1310 


8  I  9  I  10 
5  '  6 


2.9  9.4  9.7  10.4  11.5  11.7  12.31  12.0 
5440  17620  18190  19500  21560  21940  23060  22500 


0.9 
1690 


1.6 
3000 


-0.5 
-WO 


0.7 
1310 


0.8 
1500 


-0.1,  -^.3  -0.3 
-190  -560  -580 


-0.3 
-560 


0.9 
1690 


0.1 
1880 


3.11  7.7 
5810  14440 


0.1 
190 


3.2 

5620 


-0.3 
-560 


0  5 
2810 


0.6 
1120 


12.2 
22880 


1.7  . 
3190|. 


3.3 
6190 


4.7  5.2  4.0 
8810'  9750  7500 


8.8!  10.4  12  2  12.4  14.4 
16500  19500  22880  23250,27000 


4.6 


-0.5 
-940 


1.6 
3000 


4.9 
9190 


0.7 
1310 


0.5 
940 


0.7| 
1310 


6.4  5.6  6.7 
12000  10500  12560 


0.3   1.0  0.6   1.1 
560  1880  1120  2060 


-0.3 
-560 


2.9;  3.1 
5440;  5810 


4.2  4.4  4  5 
7780  8250  8440 


7.0  6.3i 
13120  11810 


1.9  . 
3560  . 


5.0  . 


15 
10 


16 
DL 


9.7;  7.1  5.80 

18190  13310,  9380 

2.3  2.3I  1.3 

4310  4310  2440 


8.0 
15000 


10.61  3.2 
19880  17440 


-0.8 
-1500 


4.8  3.2 

9000!  6000 

0.6|  0.9 

1120.  1690 


3.2  4.2  -2.9 
6000.  2810-5440 


1.4 
3190 


0.4 
750 


-0.8 
-1500 


Table  XI. — Deformations  in  Inches  and  Concrete  Stresses  in 
Lb.  per  Sq.  In. 


Set 


Loadj  DL 


Gauge 
Point 
301 


302 
803 
304 
305 
306 
307 
JC8 
309 
810 


2 

3 

DL 

1 

-0.8 
-100 

1     I     2 


-0.3 
-40 


-0.7: 


0.8   -0.1 
100     -10 


-0.5 
-60 


0.1 
10, 


-0.2' 
-25 


-0.2 
-25 


0        0.5   -0.7  . 
0  60     -90  . 


-1501. 


0.1  . 
10  . 


-0.2 
-25 

-0.2; 
-25 

-0.2 
-25 

-0.7 
-90 

-0.6 
-76 


0.6. 
75,. 


-0.9'. 

-no . 


-1.61 
-200 


-1.0 
-125 


0.1 
10 

-0.8 
-100 

-0.7 
-90 

-2.8 
-350 

-0.3 
-40 

-0.9 
-110 

-0.7 
-90 

-08 

-:oo 

1.5 
190 

-03 
-40 

i 

-0.7 
-90 

-2.3 

-6.8 
-850 


-1.4 
-175 


-3.9 
-490 


0.3 
40 


-1.1 
-140 


-0  1 
-10 


11       12 


-1.2  . 
-160  . 


-1.5  . 
-190  . 


10 


-2.0 
-250 

-1.8 
-225 

-1.2 

0.3; 
40 


,^.,1. 


.1  -0.3   -0  2 
i    -40,    -25, 


-1.7   -2.6 

-210   -325   -360:  -425 


-0.1    -Oil 
-10     -10. 


-2.9   -3.4 


-3.1 
-390 


0.3 

40 


0.2 
25 


0.4  . 
50  . 


16 
DL 


-0.2 
-26 


0.2 
25 


0.5 
60 


-2.9   -0.7i  -1.6 
-360     -90  -190 


0.1 
10 


-3.2-3.9!    -.7 -2.3 

-400   -360   -340 -290 


-6.8'  -8  3    -8.6   -9.4    -8.5;  -8.7 
-850  -1040  -1075  -1175-1060-1090 


-1.8 
-225 


-5.6 
-700 


-1.7 
-210 


-5.61 
-700 


-1.4   -1.7. 
-175   -2IO1. 


-6.3    -7  9 
-790   -990 


-7.1  . 


.    -0  1    -0.4 

.1  -10  1    -50 


-7.1 
-890 


-6.2   -4.7 
-775   -590 


-0.1 
-10 


-5.1    -4  5   -2.7 
-640   -560   -340 


Digitized  by 


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Report  of  Committee  on  Reinforced  Concrete.      125 


Table  XI. — Continued. 


Set 

1 
DL 

2 

3 

1 

-0.7 

4 
1 

5 

6 

7 

8 

9 

10   1    11 

1 

12 

7 

13 

14 

15 

16 

Load 

DL 

-0.4 
-50 

0.6 
75 

-0.6 
-75 

-0.4 
-50 

-0.4 

-0.1 
-10 

0.4 
50 

-«.5 
-60 

-0.1 
-10 

-0.2 
-25 

-0.2 
-25 

0.5 
60 

-0.6 
-75 

0.5 
60 

-0.6 
-75 

0.1 
10 

2    1    3 

3 

4         5 

1 

1 
i 

8 

9 

10 

DL 

Point 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

0 
0 

-0.6 
-60 

-0.8 

-0.3 
-40 

-2.1 
-260 

-1.4 
-175 

-0.5 
-60 

-1.5 
-190 

-1.0 
-125 

-0.6 

-90 

-0.4 

-50 

-0.8 

-100 

-1.5 



1 

1 

-75 

312 

1 
-1ft 

-2.9'  -3.5 
-3601  -440 

1 

-4.1'  -5.5 
-510   -690 

1 

-1.0 

-lOO'  -225 

-135 

313 

1 
-1.3,  -1.6 
-160   -200 

-0.41  -0.8 
-60|  -100 

-1.21  -1.9 
-160   -240 

-0.9  -10 



-1.2 

1 

-150 

314 

0.1 

-190 

-1.1 
-140 

-0.6 
-75 

-0.1 
-10 

1 

10 

315 
401 



-1.3 
-160 

-10 
-125 

-3.1 
-^90 

-0.5 
-60 

-2.9   -3.6 
-360  -  460 

^).4' 

-3.9 
-490 

-3  2 
-400 

-2.4 
-300 

-3.0 
-375 

-2.1 
-260 

-1.1 

-110   -125  -  - 

-60 

'..'.'.'.\..y.'. 

-140 

402 

-0  6i  -1  6 

1 

-2.4 

-75|  -200 

-0.51  -1.0 
-60|  -125 

-I.9I  -3  2 
-240   -400 

i 

-300 

403 

-0.1 
-10 

-1.0 
-125 

0.1 
10 

-0.5 
-60 

-0.2 
-25 

-0.8 
-100 

0.2 
25 

-0.2 
-25 

-0.1 
-10 

-0.2 
-25 

-0.5 
-60 

-0.5 
-60 

-1.0 
-125 

-0.9 
-110 

-1.1 
-140 

-1.4 
-175 

-4.5 
-560 

-2.3 
-290 

-3.3 
-410 

1 
-2.4   -3.4 
-300   -425 

1 
-2.6 

-2.1 
-260 

-1.2 
-150 

-0.8 

-100 

404 

-3  2 

-325  ... 

:::::  ::.:. 

-400 

405 

0.2 
25 

-1.1 
-140 

-0.1 
-10 

-1.4 
-175 

-0.2 
-25 

-2.6 
-325 

-0.2 
-25 

-3.0 
-375 

-0.9 
-110 

-2.4 
-300 

-0.3 
-40 

-3.1 
-i390 

-1  n 

1 

-1  8 

-225 

406 

-3  3 

-410 

-0.5 
-60 

-3.4 
-425 

-2.9 
-360 

-0.7 
-90 

-3.5 
-440 

-3.1 
-390 

-0.9 
-110 

-3.8 
-475 

1 
-2.9,  -2.9 
-360'  -360 

1 
-0.8,  -1.6 

-no:  -200 

1 
-3.7,  -4.7 

-460,  -590 

1 

-3.2 
-400 

-2.7 
-340 

-2.4 

-300 

407 

-1.6 



-200 

408 
400 

-4.7 
^90 



-3.6 
-450 

-2.6 
-325 

-1.9 
-240 

-1  5 

j 

-190 

410 

-0.5 
-60 

-0.7 
-W 

-0.6 
-75 

-0.3 
-40 

-0.2 
-0.6 

-2  5 

-9.  7 

-3.1 

-390 

-3.4  -3.6 
-425 1  -450 

1 

-4  5 

-1.0 

-310;  -340 

-560 

125 

411 



-1.1 

1 

'       1 

:::::  ::::: 

-140 

412 
413 

-3.2'  -3.3 
-4001  -410 

-1.5'  -2.0 
-1901  -250 

'h).8 

1  -100 

-1.4'  -1.4 
-175|  -175 

1 

-3.8'  -3.4  -4.0 
-4751  -I25I  -.500 

-2.6   -2.7,  -3.3 
-325'  -340l  -410 

-1.3   -0.9,  -0.8 
-160'  -110|  -100 

-1.9'  -2.4|  -3.1 
-240|  -3001  -390 

i 

-1.4I 

-650| 

1 

-3.8 
-475 

-2.4 
-300 

-1.6 
-200 

-1.6 

-75[  -125 
-0.5'  -0  8 

-200 

0.2 
25 

-1.6 
-200 

0.1 
10 

414 



! 

-60 

-0.4 
-50 

-0.1 

-100 

-0.7 
-90 

-0  ? 

415 
417 

-0.2 
-25 

-0.1 

-0.7 

-3.2 
-400 





-2.6 
-325 

-1.7 
-210 

-"1 

-10     -25 

i""[ 

.........j.   ...  .......... 

Digitized  by 


Google 


126     Report  of  Committee  on  Reinforced  Concrete. 


0 — 0 — d  MM y 

Un/t  Tension  in  Jteei 


I 


400* 

) 

j 

=*, 1 

{ 

,/ 

n 

/ 

/ 

1 

r 

/ 

/ 

/ 

0* 

0    ic 

00    0     5000 

[»7        , 

0     5000 

ifd      1 

0    5000 

\or 

1     5000 

Unit  Tension  in  sreel 


^  400 
^JOO 
5  ?00 
I  /OO 
S        0 


p    I  J    -i      t 

~-  t     X     t 

r^          ^  4  -  t 

ST 
^500 

5     ?«> 


/OO 


•^       0 


107 


loe  I09 


ikW" 


/// 


unit  5fre55  in  5tee\ 


3^ 


115 


114 


\II5 


-TSSr 


^400 


^00^ 
500 


1  /a? 

S       0 


//7 


_L 


('     3000 


M 


z. 


116. 


J- 


I 


IZO 


-L 


6000     0      MOO 


Unit  3tre3S  in  3teel 
FIQ.   51. — LOAD-DEFORMATION  DIAGRAMS  FOR  REINFORCEMENT. 


Digitized  by 


Google 


Report  of  Committee  on  Reinforced  Concrete.      127 


o    3600   6  foooo 

Unit  Tension  in  3feel 


^400 


I  /oo/- 


I 


f 


ZIO 

-1- 


ZIZ 


6^  tOtOOO    b  MXXX)     O      5000 

Unit  Tension  in  3teel 


?I6 


O       to       20     30      '40 

Distonce  from  Capital  in  Inches 


^400 


2  Joo 
I     o 


< 

v\ 

1 — ^\ 

r 

/ 

J 

f 

J 

/ 

J 

^ 

^ 

M 

y 

/ 

Z 

Z 

i^zta 

( 

"^ 

6    A 

Unii 

^  3tr 

ess 

AM 

in  Jj 

^eel 

m 

IM   I 

)      t 

}6t 

WO 

tdi 

\dd 

Unit  Stress  in  Steel 

PIG.  62. — LOAD-DEFORMATION  DIAGRAMS  FOR  REINFORCEMENT. 
READINGS  AND  CURVES  BY  W.   A.   SLATER. 

Digitized  by 


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128     Report  op  Committee  on  Reinforced  Concrete. 

to  trace,  and  were  only  of  such  magnitude  as  would  be  expected 
to  accompany  the  reinforcement  stresses  observed. 


^500 
S  zoo 


Unit  Compression  //?  Concrete 


too 
0 


y 

\T 

/ 

I 

L 

1 

/ 

1 

I  \ 

9    .,/ 

^1 

> 

3/s 

? 

u 

11 

dA 

»    c 

)    5 

00     i 

■>    A 

00    c 

3t 

30      C 

)       300      C 

>       600 

Unit  Compression  m  Concrete 


Unit  Compression  in  Concrete 

Fia.   53. — ^LOAD-DEFORMATION  DIAGRAMS  FOR  CONCRETE. 


Examination  of  the  plotted  deflections  and  stresses  shows  a 
change  of  inclination  of  the  curves  at  a  load  of  200  lb.  per  sq.  ft. 
Take,  for  instance,  point  202,  which  is  typical  of  this  condition. 


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Repobt  of  Committeb  on  Reinfobced  Concrete,     129 

At  200  lb.  per  sq.  ft.  the  stress  in  this  bar  was  14,000  lb.  per  sq.  in.; 
the  load  producing  this  stress  was  that  of  stage  3. 


Unit  Compression  in  Concrete 


4aL 


fam    loos 


JUX) 
;  300 


Ebb    6    Ad    6    ido    5 
Unit  Compression  In  Concrete 


407     4408 


So- 


J40i\ 

o     soo 


I 


I  ^^f—l — T 

:^        \40§      \4IC 

«     %    lo    h    A 


\4II 


300 


Wt 


6    SCO    o    355    0    soo    o    soo' 
unit  Compression  in  Concrete 


1 4/3       \4K      \4/5\ 
>    soo   0    500   o    soo' 


FIQ.  54. — LOAO-DBFOBMATION  DIAGRAMS  FOR  CONCBBTB.     RBAAINQ8 
AND  CURVES  BT  W.  A.  SLATER. 

When  the  load  from  the  adjoining  panels  was  shifted  and  cor- 
responded to  400  lb.  per  sq.  ft.,  the  stress  was  only  19,000  lb.  per 
sq.  in.,  instead  of  some  32,000  obtained  by  producing  the  curve  to 


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130     Report  of  Committee  on  Reinforced  Concrete. 

the  400  lb.  line  at  that  slope  which  obtained  below.  This  indicates 
that  a  part  of  the  load  is  carried  by  the  panels  adjoining  the  loaded 
one. 

The  same  result  is  indicated  in  the  case  of  point  104,  which 
is  at  the  bottom  of  the  slab  near  the  middle  of  one  of  the  panels. 
The  fact  that  the  adjoining  panels  assist  in  carrying  a  loiad  placed 

Table  XII. — Summary  op  Stresses. 


Location. 

Gauge 
Point. 

Design  Load, 
200  lb.  per  sq.  ft. 

400 
lb.  per«q.  ft. 

D.L.* 

L.  L. 

Total. 

L.  L. 

Total. 

Reinforcement  Streui 
Over  Column  Head 

Long  Span 

202 
204 
Av. 

2.000 
2.500 
2.250 

14.000 
17.500 
15.750 

16.000 
20.000 
18.000 

19.000 
23.000 
21.000 

21,000 
25.600 
23,260 

Short  Span 

201 
206 
Av. 

1.500 
1,000 
1.250 

3.000 
3.000 
3.000 

4.500 
4.000 
4.250 

7,000 
1,000 
8,600 

8,600 
11.000 
9,750 

Bottom  of  Slab  at  Side  of 
Panel 

Long  Span 

102 
112 
Av. 

1.000 
1.600 
1.250 

7.000 
11.500 
0.250 

8.000 
13.000 
10.600 

9.000 
13.600 
11.260 

10,000 
15.000 
12.500 

Short  Span 

101 

500 

1.000 

1.500 

4.000 

4.600 

Bottom  of  Slab  at  Middle  of 

Long  Span 

104 
122 
Av. 

500 

1.000 

750 

7.500 
4.000 
6.750 

8.000 
6,000 
6.500 

12.000 
9.600 
10.760 

12.600 
10.600 
11.600 

Panel 

Concrete  Streaees, 
Bottom  of  Slab  at  Colxmm 

Short  Span 
Long  Span 

103 
109 
Av. 

306 

500 

1,000 

750 

100 

1.500 
2,500 
2.000 

750 

2.000 
3,500 
2,750 

850 

8.000 
6.600 
7.260 

1.060 

8.500 
7.500 
8.000 

1.160 

Short  Span 

315 

100 

250 

350 

450 

660 

Top  of  Slab  at  Edge  of  Panel 

Long  Span 

406 
412 
Av. 

100 
100 
100 

300 
400 
350 

400 
500 
460 

360 
600 
426 

460 
600 
625 

Top  at  Middle 

408 

150 

400 

660 

600 

750 

Bottom  of  SUb  at  Wall 

Long  Span 

302 
304 
Av. 

50 
100 
75 

150 
250 
200 

200 
350 
275 

260 
400 
326 

300 
600 
400 

*  Dead-load  Btreases  obtained  from  atreas-deformation  curves  by  projecting  curve  down  to 
no-load  line. 

on  one  panel  is  also  shown  by  the  fact  that  deflections  were  ob- 
served in  panels  adjacent  to  those  loaded^  as  shown  in  Fig.  48 
and  by  the  fact  that  cracks  on  the  under  side  of  the  slab  were 
traceable  well  past  the  middle  of  panels  adjoining  these  loads. 

The  point  of  contraflection  was  foimd  to  be  at  0.21  of  the 
clear  span  from  the  edge  of  the  column  head. 


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Report  op  Committee  on  Reinforced  Concrete.      131 


FIG.  55. — PLAN  SHOWING  LOCATION  OF  CRACKS.   FULL  LINES  INDICATE  CRACKS 
ON  TOP  AND  DOTTED  LINES  ON  BOTTOM  OF  SLAB. 


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132     Repobt  op  Committeb  on  Reinfobced  Concrete. 


.  Mm 


FIQ.   66. — BARR  BUILDINQ  TEST  PANEL,   ST.   LOUIS,  MO. 


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Repobt  op  Committeb  on  Reinforced  Concbete.     133 

The  high  values  of  bond  stress  observed  indicate  that  con- 
sideration be  given  to  this  feature  in  the  design  of  flat  slabs, 
especially  when  it  is  realized  that  no  matter  what  scheme  of  rein- 
forcement be  adopted  there  will  exist  stresses  at  right  angles  to 
any  given  bar  over  the  column  which  tend  to  destroy  the  adhesion 
of  the  concrete  to  the  reinforcement. 

Part  III.     Test  op  a  Concrete  Floor  Reinforced  in  Two 

Directions. 

Test  Panel — ^The  test  was  made  on  a  panel  representing  a  wall 
panel  of  a  continuous  floor  and  to  approximate  existing  conditions, 
cantilevers  were  built  on  3  sides.     These  cantilevers  were  loaded 


FIG.  57. — BARB  BUILDINQ  TEST  PANEL  WITH  LOAD  OF  380  LB.  PER  SQ.  FT. 

during  the  test  until  the  tangents  to  the  slab  over  the  supporting 
beams  became  approximately  horizontal,  as  would  be  the  case  in  a 
continuous  floor  under  multiple  panel  loading. 

The  panel  proper  is  25  ft.  long  by  26  ft.  9  in.  wide,  Fig.  56; 
and  is  carried  by  steel  I  beams,  fireproofed  with  concrete.  These 
beams  rest  on  steel  bearing  plates  on  concrete  posts  at  each  comer 
of  the  panel.  Seven-inch  tile  was  used  with  a  cover  of  2J  in.  of 
1:1^:3  concrete,  making  the  total  thickness  of  the  slab  9 J  in. 

The  arrangement  of  tile  is  such  that  when  alternate  rows  of 
block-tile  and  channel-tile  are  laid,  the  concrete  is  formed  into 
two  series  of  intersecting  T  beams,  spaced  15  in.  centers  each  way 
and  having  3-in.  steins.    Small  furring-tile,  laid  at  the  intersection 


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134     Repobt  op  Committbb  on  Rbinporcbd  Concrete. 

of  the  ribs  thus  formed,  complete  the  tile  ceiUng  surface.  The 
panel  was  remforced  as  shown  m  Fig.  56,  designed  for  a  live  load 
of  150  lb.  per  sq.  ft. 

The  panel  was  poured  on  September  1, 1911,  imder  unfavorable 
conditions,  it  being  necessary  to  carry  on  a  considerable  portion 


PIQ.   58. — PLAN  SHOWING  METHOD   OF  LOADING   BARR  BUILDING  TEST  PANEL. 

of  the  work  after  dark.  The  weather  was  very  hot  during  the 
next  few  days  and  several  of  them  were  holidays,  so  that  the  slab 
was  not  even  kept  wet.  On  the  whole,  conditions  under  which 
this  slab  was  erected  were  probably  not  more  favorable  than  would 
exist  in  an  actual  building. 


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Report  of  Committee  on  Reinforced  Concrete.     135 

Method  of  Testing. — Sand  in  sacks  was  used  for  the  load, 
Fig.  57,  each  sack  being  filled  on  the  scales  to  weigh  100  lb.  The 
loading  was  started  on  November  23,  1911,  and  progressed  by 
stages,  alternating  with  readings,  until  650  lb.  per  sq.  ft.  was 
reached  on  December  6,  1911.  The  test  was  stopped  at  this 
point  because  of  the  expense  involved  in  placing  the  load  upon 
the  high  piles  of  sacks.  The  total  load  remained  in  place  on  the 
panel  for  48  hours,  after  which  unloading  was  started  and  completed 
5  days  later. 

Table  XIII. — Stages  op  Loading. 


Time  of  Loading. 

Load  in  lb 

periQ. 

ft. 

Stefe. 

Gantileve 

tm 

Start. 

Finiflh. 

Panel. 

Left. 

Rear. 

Rilht. 

1911 

1911 

1 

Nov. 

23.    2.30  p.m. 

Nov. 

24,  10.00  A.  M. 

75.5 

38.3 

38.6 

39.4 

2 

Nov. 

25,  11.00  A.  M. 

Nov. 

25.    3.30  p.m. 

76.5 

74,3 

70.3 

74.3 

3 

Nov. 

27,    2.00  p.  M. 

Nov. 

27.    4.00  p.m. 

75.5 

93 

98.2 

93 

4 

Nov. 

28.  12.30  p.  M. 

Nov. 

28.    6.30  p.m. 

150 

183.5 

194.2 

191.5 

5 

Nov. 

29.  12.30  p.  M. 

Nov. 

29.    5.20  p.m. 

247 

183.5 

194.2 

191.5 

6 

Nov. 

30.    1.00  p.m. 

Nov. 

30.    4.50  p.m. 

300 

183.6 

247 

191.5 

7 

Dec. 

1.  10.00  A.  M. 

Dec. 

1.    2.10  p.m. 

300 

300 

298 

300 

8 

Dec. 

1.    4.30  p.m. 

Dec. 

1,    6.15  p.m. 

300 

346 

298 

346 

9 

Deo. 

2.    9.30  a.m. 

Dec. 

2.    9.50  a.m. 

300 

372 

298 

372 

10 

Dec. 

2,  10.00  A.  M. 

Dec. 

2.  10.15  A.  M. 

300 

385 

298 

385 

11 

Dec. 

2. 

Dec. 

2.  12.05  p.  M. 

300 

385 

298 

385 

12 

Dec. 

3,    9.00  a.m. 

Dec. 

3.    9.45  a.m. 

300 

385 

298 

385 

13 

Dec. 

3.    9.00  a.m. 

Dec. 

3.    2.00  p.m. 

380 

465 

376 

465 

14 

Dec. 

5,  10.30  A.  M. 

Dec. 

5.    4.00  p.m. 

500 

465 

376 

465 

15 

Dec. 

6.    9.40  a.m. 

Dec. 

6.  10.40  A.  M. 

527 

465 

376 

465 

16 

Dec. 

6.  11.20  A.  M. 

Dec. 

6.  12.15  p.  M. 

550 

465 

376 

465 

17 

Dec. 

6.  12.50  p.  M. 

Dec. 

6.    1.35  p.m. 

567 

465 

376 

465 

18 

Dec 

6,    2.10  p.m. 

Dec. 

6.    3.00  p.m. 

591 

465 

376 

465 

19 

Dec. 

7,    8.00  a.m. 

Dec. 

7.    9.20  a.m. 

615 

465 

376 

465 

20 

Dec. 

7.  10.60  A.  M. 

Deo. 

7.    1.10  p.m. 

650 

465 

376 

465 

Both  reinforcement  and  concrete  stresses,  as  well  as  deflec- 
tions, were  measured  throughout  the  test,  exceptionally  complete 
sets  of  readings  being  taken  imder  the  design  load  of  150  lb.  per 
sq.  ft.  and  under  the  test  load  required  by  the  City  of  St.  Louis, 
t.  e,,  a  superimposed  load  equal  to  once  the  dead  load  plus  twice 
the  live  load,  or  380  lb.  per  sq.  ft. 

Deflections  were  read  by  measuring  the  distance  between  a 
steel  plate  fastened  to  the  ceiling  and  a  steel  rod  held  in  a  scaffold 
below.  An  inside  micrometer  reading  to  0.001  in.  was  used,  both 
plate  and  rod  having  countersunk  holes  to  locate  exactly  the  posi- 
tion of  the  instrument. 


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136     Report  of  Committee  on  Reinforced  Concrete. 

The  stresses  in  the  remforcement  were  read  by  an  exten- 
someter  which  is  a  modification  of  the  Berry  Strain  Gauge  used  to 
read  stresses  on  the  concrete,  while  W.  A.  Slater  read  reinforcement 
stresses  with  a  modification  of  the  Berry  Strain-Gauge,  made  at 


FIG.   59. — PLAN  SHOWING  LOCATION  OP  DEFLECTION  POINTS. 

the  University  of  Illinois,  Figs.  1  and  2.  Both  of  these  instruments 
have  points  which  are  inserted  into  small  holes  drilled  in  the  steel 
or  in  metal  plugs  set  in  the  concrete  and  read  directly  to  1/5000 
of  an  inch,  or  by  estimation  to  one  quarter  of  this  amount.     An 


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Report  op  Committee  on  Reinforced  Concrete.     137 


Table  XIV.- 

-Deflections,  Barb  Building  Test  Panel. 

Unit 
Load. 

76.5;  150 

300 

300 

380 

380     500 

500 

627 

550 

567 

591 

615 

660 

Deflec 

tiOD 

Pomt 

Stage. 

3 

4 

6 

11 

13 

13 

14 

14 

15 

16 

17 

18 

19 

20 

Date 
and 
Hoar. 

^i 

ii 

1^ 

•^1 

ii 

11 

1= 

4 

•  si 

^3 

1 

.354 
.266 
.198 
.153 
.130 
.117 
.110 
.127 
.142 
.134 
.296 
.213 
.160 
.104 
.094 
.089 
.078 
.086 
.090 
.091 
.071 
.054 
.043 
.034 
.024 
.019 
.022 
.025 
.030 
.116 
.098 
.082 
.075 
.068 
.073 
.068 
.072 
.082 
071 
.063 
.054 
049 

".Hi 

.903 
.724 
.559 
.428 
.420 
.421 

1.340  1.417!l.456 
1.043{1.099ii  2lfl 

1.456 
1.216 
1.017 
.870 
.952 
1.167 
1.332 
1.631 
1.921 
2.155 

2 

3 

.794     831 

4 

.591 
.567 

.611 

.581 
.568 
.658 
.778 
ROT 

5 

6 

7 

.480;   .645 
.568'     764 



8 

9 

.645 
.693 
.860 
.598 
.438 
.302 
.317 
.310 
.352 
.408 
.460 
.067 
.402 
.331 
.265 
.205 
.172 
.148 
.154 
.165 
.179 
.530 
.448 
.362 
.293 
.262 
.244 
.238 
.204 
.248 
.386 
.324 
.260 
.202 
.177 
.159 
.167 
.186 
.202 

.878 



20 

.9601   .982 
1  153i 1.222 
.890'   .940 
.6361   .668 
.419,   .438 
.424)   .434 
.4101   .417 
.468,   .478 
.5461   .558 
.622|   .633 
.073    .078 
.5441   .553 
.4441   .453 
.354    .358 
.268    .274 
.234    .247 
.228'   .239 
.2711   .290 
.330,   .355 
.3941   .431 
.7251   .742 
603      616 

10 

11 

12 

13 

14 

15 

1 

16 

. 

17 

1 

18 

1 

19 
21 

Col. 

.02 

.100    .103 

.107 

.109 

.114 



.126 

.137 

22 

23 

24 

25 



26 

27 

'28 

29 

30 

31 

32 

.477 
.376 
.351 
.351 
.373 
.415 
.467 
.527 
.432 
.338 
.251 
.228 
.232 
.263 
.324 
.880 
.066 
.155 
.900 

.488 
.384 
.361 
.366, 
.3921 
.442 
.502 
.545 
.446 
.347 
.258 
.238 
.2451 
.285, 
.3501 
.414 
.068 
.1581 

02fi 

33 

34 

35 

I"": 

36 





87 



38 

39 

40 

41 

42 



43 

046 

44 

.053 
.064 
.079 
.095 
.016 
.042 
.104 
.274 
.124 
.229 
.013 
.071 

45 

46 

47 

!!.!.  :.... 

48 
49 
60 

Col. 

.003 
.027 

.033'   .047 
.118,   .119 

'   .643 

.7741   .925 

.72.'5 

.085 
.264 

.087    .094    .095 
.2741   .2941   .324 

■     1- 

.099 
.348 

.103 
.379 

.107 
.414 

.115 
.409 

51 
52 

Center 

.129 

1.29911.331,1.947 
.993  1  0171 

2.6192. 163'2. 327 

1...     1.     . 

2.444 

2.658 

2.897 

3.313 

53 
54 
55 

Col. 

"cor* 

.009 
.040 
.039 

.152 
.211 
.114 

.127 
.335 
.078 

.148 
.434 
.105 

.154 
.449' 

.113| 

.162 
.535 
.130 

.175    .176,   .171 
.5451   .56ll   .586 
.136|   .139    .143 

.170 
.601 
.147 

.175 
.627 
.150 

.190 
.659 
.158 

.196 
.702 
.165 

:::::i::::: 

1 

1 

51 

Corr 

1 

0.080 

.167 

.594 

.641 

.920 

.9441.459 

l.sie 

1.632 

1.777 

1.872 

2.052 

2.252 

2.608 

Laat  line  of  readings  are  deflections  at  center  of  panel  assuming  supporting  beams  to  be  rigid.    All 
other  readingB  eorrected  for  pier  settlement  only. 


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138     Report  op  Combiittee  on  Reinforced  Concrete. 

8  in.  gauge  length  was  used  throughout  the  test.  The  length 
of  such  an  instrument  varies  with  changes  of  the  temperature  of 
the  observer's  hands,  to  correct  for  which  readings  were  taken  at 
intervals  on  standard  bars  and  all  temperature  corrections  neces- 
sary have  been  applied  to  the  stresses  given  in  the  tables  and 
plotted  in  the  curves. 

Method  of  Loading. — To  prevent  the  possibility  of  the  load 
arching,  the  sacks  of  sand  were  arranged  in  separate  piles,  as 


&50 

^ 

^^ 

^^^ 

^ 

,^' 

--" 

^ 

^ 

_^ 

^ 

J>^' 

A/)/) 

^ 

^ 

<: 

^ 

y 

^ 

0\iftlO 

(S 

p\ 

W 

A 

/^ 

A 

P 

A 

K 

/ 

^JMD 

/mi 

J 

^U 

L_& 

p.SL±U 

^1 

rstLoad 

a«^^c 

J 

T 

^y 

.^ 

|5<» 

^ 

6 

/ 

/ 

/ 

/ 

/ 

Curve  /  5ha¥5  defk 

ortlon  of  h 

Hp 

V 

r    - 

siqn 

Lope 

1 

center  of  the  panel  wilt)  reelect  to 
the  columns. 

Curve  t  shows  deflection  of 
Jhe  center  of  the  panel  with  respect 

S/oo 

f 

>«4 

to  the  supporting  beams 

.       1       .       1       1       1 

^Xl. 

c 

ilea 

4    d. 

6    d. 
in 

6    / 
/nch 

ea. 

/ 

0 

3. 

0 

FIG.  60. — DEFLECTIONS  AT  CENTER  OF  PANEL. 

shown  in  Fig.  57.  The  wide  aisles,  Fig.  58,  were  necessary  for 
the  accommodation  of  the  instruments  and  observers.  Table 
XIII  gives  the  loading  on  the  various  portions  of  the  panel  at 
different  times,  as  well  as  the  loads  per  square  foot  of  slab  and 
cantilevers  and  the  date  and  hour  at  which  each  stage  was  started 
and  completed.  The  loads  per  square  foot  are  in  each  case 
obtained  by  dividing  the  total  load  on  the  panel  or  cantilever  by 
the  area,  the  intensity  of  load  under  the  piers  being  much  greater. 
Up  to  the  test  load  required  by  the  City  of  St.  Louis  the 


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Repobt  of  Committee  on  Reinforced  Concrete.     139 


Deflection  Points 

QJS^XJfM^XJl  JO 


Deflection  Curve  along  Center- line  of  Panel  in  Direction  of  long  Span 
Under  Design  load  {I50*per  x^n) 
Deflection  Points 


fl  J 

«J 

7  S 

6  S 

5  34  33  S 

r  s 

JO 

A 

3t                          34 

^ 

^ 

' 

> 

% 

^ 

y' 

\ 

y 

did 

K                                                       ^ 

^       \ 

X                          # 

^       1 

•^ 

V                w, 

/               !^ 

1-0 

'^ 

>v            J? 

y             « 

I.I 

^s. 

" 

^ 

>^k          1 

/« 

^^ 

.1 

Deflection  Cunn  along  Center- line  cf  Panel  In  DIrectloh  of  long  Joan 
under  Test  Load  required  by  the  3t  Louis  DIdg  Code  (5acrperjif.fr.) 

WIQ.  61. — ^DEFLECTION  CXTRYE  IN  DIRECTION  OF  LONG  SPAN. 


1     i 

ilea 

Pomtj 

3    i 

r     f 

10                      a/                       s 

0                              4« 

L 

\ 

^ — 1 

r^ 

-r 

< 

^      1 

^^ 

i 

.50 

J 

/ 

% 

I 

V 

Dm 

flection 

Cm 

rve 

a/a 
una 

u 

\iisign  lSoS (lOL 

^;jr"4^'^' 

Tf  Short  span 

1   J 

)efk 

vtk) 

nPi 

vnt. 

f 

5    7    i 

>    s 

}    I 

D 

£ 

V 

s 

0 

^ 

9 

.to 

_^ 

y 

X 

/ 

— 

M^l 

•k 

. 

/ 

70 

/ 

■^ 

s 

> 

/ 

r 

> 

B 

^         \ 

/ 

2i 

•4g 

/          \ 

E 

f 

^ 

y 

**» 

uo 

LtO 

^ 

^ 

v^ 

^ 

/JO 

Defkchon  Curve  along  Center- line  of  f^jnet  in  Dined  fop  of3hort  Span 
under  Test  load  required  fy  the  St.  Louis  3/dg  Code(3d0^prs(f.ft) 

FIQ.  62. — ^DEFLECTION  CURVE  IN  DIRECTION  OF  SHORT  SPAN. 


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140      ReFOBT  of  ComUTTEB  ON  ReINFORCEO  Ck)NCRIiTB. 

cantilevers  were  carefully  loaded  to  horizontality,  but  from  this 
stage  on  no  more  load  was  applied  to  the  cantUevers  and  they 
rose  slightly,  thus  increasmg  the  deflection  at  the  center  of  the 
panel. 


I--!- Kr-««"B55— B» ^ 


gHDnnnnnniiBannnnDD 
TinDDDnnnnnnnnDnnnn 
DnDnnDDnnDnnnDDDnd 
DnDnnDnDDDnnnnnDn 
nnnnnDDnDDnnnnDDDD 
nnDnnnnDDDnnnnDnnn 
DDDDnDnnDDnnDnnDD 
nnnnnnnDDDnnDDnnaD 
DnnDnDDDDDnDnDnDD 
nnannnDDDDDnnDnDnL 

•-•  Indicates  Points  onfop  of  Slab. 
o-o  Indicates  faints  onBoltomafSab 


aDDDDDDaDDDDDnnDa 

nnnnnnnnnnDnnnnnn 
DaDnanDDnnnnnnnDD  ., 
DDanDDnnnnDnnDDnnngj 
pnnnnnDnnDnDannnnn^ 
DDnannnnnnnnnDnnna 

DDDDDDDDQDDDDDDDD 

^nDnannnnaDDnnnnnn 


no.   63. — PLAN  SHOWINQ  LOCATION  OP  GAUGE  POINTS  ON  CONCRETE. 

The  horizontality  of  the  tangents  over  the  beams  was  deter- 
mined by  measuring  deflections  of  both  the  slab  and  cantilevers 
at  a  series  of  points  along  a  line  perpendicular  to  the  beams. 
The  deflections  were  then  plotted  and  a  smooth  curve  drawn 


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Report  of  Committee  on  Reinforced  Concrete.     141 


which  showed  at  a  glance  whether  or  not  horizontality  existed. 
It  was  often  found  necessary  to  shift  the  load  on  the  cantilevers 
several  times  before  the  correct  amount  and  position  were 
reached. 


.40) 


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FIG.  64. — ^DIAGRAM  OF  STRESSES  IN  CONCRETE. 


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Deflections. — Deflections  were  read  at  the  points  shown  in 
Rg.  69.  A  summary  of  the  observations  is  given  in  Table  XIV. 
There  was  a  settlement  of  the  footings  which  has  been  corrected 
for  in  the  summary  and  in  the  curves. 


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142     Report  of  Committee  on  Reinforced  Concrete. 

The  center  point  deflections  are  plotted  in  Fig.  60.  The 
deflections  shown  by  the  curves  represent  the  deflections  of  the 
panel  with  respect  to  the  supporting  beams.  In  order  to  arrive 
at  the  deflection  of  the  panel  proper,  the  gross  deflections  were 
decreased   by  an  amount    equal  to  the    average   deflection   of 


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PIG.   65. — STRESS-STRAIN  DIAGRAM   OF  TWO  CONCRETE  TEST  CYLINDERS. 

the  supporting  beams.  Curve  1  shows  the  gross  deflections, 
the  dotted  curve  including  settlements  occurring  during  the 
intervals  between  loads  and  the  solid  line  giving  the  true  elastic 
deflections  (including  beam  deflections)  caused  by  a  uniform  rate 
of  loading.    The  dotted  portion  of  Curve  2  ehows  the  same  thing 


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Report  of  Committee  on  Reinforced  Concrete.     143 

after  correcting  to  a  uniform  rate  of  loading.  The  solid  line, 
Curve  2,  should  be  used  in  comparing  this  test  with  others  or  as 
a  basis  for  deflection  coefficients. 


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•-•  Indicates  Points  on  Top  of  Slab 
oo  Indicates  Points  on  bdttom  of5lab . 


PIQ.    66. — PLAN   SHOWING   LOCATION   OP   GAUGE    POINTS   ON   REINPORCEMSNT. 

Fig.  61  shows  exaggerated  scale  sections  of  the  panel  along 
the  long  axis  for  the  design  load  and  for  the  load  specified  by  the 
St.  Louis  Building  Laws.  The  deflections,  from  which  these  are 
plotted,  are  corrected  for  settlement  of  the  footings  only.    Fig.  62 


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144     Report  op  Coboiittee  on  Reinforced  Concrete. 

shows  similar  sections  along  the  short  axis  of  the  panel.  Inspec- 
tion of  these  figures  will  show  that  the  cantilevers  were  properly 
loaded  to  obtain  horizontal  tangents  over  the  supporting  beams. 
Deformations  and  Stresses. — Concrete  stresses  were  read  at- 
the  points  shown  in  Fig.  63.  A  summary  of  the  observed  stresses 
is  given  in  Table  XV;  the  loadnstress  curves  at  a  few  of  these 
points  are  plotted  in  Fig.  64.  In  these  curves  and  in  the  sum- 
mary, the  stresses  are  those  which  were  induced  in  the  concrete 
by  the  loads  greater  than  75  lb.  per  sq.  ft.  At  this  stage  the 
points,  at  which  these  stresses  were  read,  worked  loose  and  had 
to  be  reset. 


Table  XV.— Concrete  Stresses,  Barr  Building  Test  Panel. 

Unit 
Load. 

150 

150 

160 

800 

380 

880 

Gaufce 
Point 

Stage. 

4 

4 

4 

11 

13 

18 

Date 

Nor.  28 

Nov.  29 

Nov.  29 

Dec.  2 

Dec.  3 

Dec.  4 

and  Hour. 

7  p.m. 

10  A.M. 

12  m. 

12  m. 

8.30  p.  M. 

9.30  p.m. 

401 

R.O. 

-40 

-285 

-81 

-625 

-796 

-765 

402 

R.O. 

+40 

-162 

+  122 

-430 

-422 

-422 

801 

R-0. 

—195 

—195 

—203 

—943 

—1225 

—1322 

803 

R.O. 

-195 

-504 

-211 

-1005 

-1322 

-1370 

805 

R.O. 

-105 

-350 

-57 

-740 

-935 

-1022 

802 

R.O. 

-26 

-858 

-57 

-723 

-870 

-967 

804 

R.O. 

-122 

-382 

-162 

-796 

-1022 

-1095 

808 

R.O. 

-58 

-252 

-73 

-1005 

-862 

-926 

810 

R.O. 

+65 

-219 

+130 

-740 

-796 

-943 

807 

R.O. 

+146 

-471 

+90 

+130 

+365 

+211 

809 

R.O. 

-49 

-398 

-81 

-292 

-220 

-374 

811 

R.O. 

-80 

-325 

+0 

-560 

-480 

-600 

+  as  Tension. 
—  »Compreimon. 

The  reduction  in  stress  with  increasing  load  appearing  in 
some  of  the  curves  may  be  the  result  of  the  gradual  giving  away 
of  the  concrete  in  tension  and  resulting  shifting  of  the  point  of 
inflection. 

Two  test  cylinders  8  x  15  in.  were  taken  from  the  mixer  at 
the  time  the  slab  was  poured  and  after  being  cured  under  the 
same  conditions  as  the  panel  itself,  they  were  tested  just  after 
completion  of  the  readings  on  the  panel.  The  ultimate  strength 
and  the  modulus  of  elasticity  of  these  were  widely  different  as 
can  be  seen  from  the  stress-strain  diagrams  in  Fig.  65.  In  deriv- 
ing the  concrete  stresses  the  average  modulus  was  used,  being 
taken  at  3,250,000. 


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Report  of  Committee  on  Reinforced  Concrete.     145 


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Report  op  Committee  on  Reinforced  Concrete.     151 

Fig.  66  shows  the  location  of  gauge  points  at  which  reinforce- 
ment stresses  were  read.  A  summary  of  the  observed  stresses  is 
given  in  Table  XVI,  together  with  the  load  and  time  at  which 
each  set  was  taken.  The  two  figures  given  for  each  point  are 
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curves  for  a  few  of  the  bars  at  critical  points  and  for  the  struc- 
tural steel  supporting  beams. 

Fig.  69  shows  the  distribution  of  stress  in  the  bars  which  are 
on  the  short  span.  The  section  shown  is  taken  along  the  long 
axis  of  the  panel  and  the  stresses  plotted  are  those  in  the  bars 
cut  by  the  section.    Similar  curves  are  shown  in  Fig.  70  for  the 


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no.   69. — ^DISTRIBUTION   OF   STRESS  IN   THE   REINFORCEMENT   CABBTING   THE 
LOAD  ACROSS  THE  SHORT  SPAN. 


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Report  of  CoMinTTEE  on  Reinforced  Concrete.     153 

top  bars  over  the  supporting  beams.  Some  of  these  curves  may 
be  distorted  because  the  supporting  beams  tipped  up  on  the 
bearing  plates  and  spread  apart  at  the  comers,  thus  inducing 
tension  across  the  diagonals  of  the  slab. 


V. '    .        *".4.'.'.;.".'-'^».v.m.nijr»...^.ni.i  i.-;.-.i'.i.^\-.n-'.  .■.,*■•■■..>.•  ...I...  ■..'•'•••  .'..S-'V  ^»     '.*.■.'■•  i-.  ■■'  •'•1*1 


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FIQ.   70. — DIAGRAMS  SHOWING  DISTRIBUTION  OF  REINFORCEMENT  STRESS. 

At  the  500-lb.  load,  cracks  could  be  found  extending  a  short 
distance  from  the  comers  of  the  panel  along  the  diagonals. 
Pig.  71  shows  the  location  of  cracks  at  a  load  of  660  lb.  per  sq.  ft. 


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154     Report  op  Committeb  on  Reinforced  Concrete. 

In  order  to  locate  the  points  of  inflection  and  to  determine 
the  bond  stresses;  readings  were  taken  along  portions  of  three 
bottom  bars.  The  results  of  these  readings  are  plotted  in  Figs. 
72  and  73. 


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FIG.   71. — PLAN  SHOWING  LOCATION  OP  CRACKS. 

A  summary  of  the  stresses  and  deflections  at  the  critical 
points  of  the  slab  is  given  in  Table  XVII. 

No  definite  conclusions  as  to  the  distribution  of  stress  among 


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Report  of  Cobimittee  on  Reinforced  Concrete.     155 


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no.  72. — VARIATION  OF  STRESS  AND  LOCATION  OF  POINT  OF  INFLECTION  ALONO 
MIDDLE  BAR  IN  DIRECTION  OF  SHORT  SPAN. 


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156     Report  of  Committee  on  Reinforced  Concrete. 


Table  XVII. — Summary  of  Principal  Stresses  and  Deflections,  Barr 
Building  Test  Panel. 

Deflections  at  Cbnteb. 


Design  Load  160  lb.  per  sq.  ft. 


St.  Louis  Building  Code  380  lb.  per  sq.  ft. 


0.167  in.,  or  j^„  of  Spian 


0.860  in.,  or  gf,  of  Span 


CoNCBBTB  Stresses. 

[>de 
l.ft. 

Gauge 
Point. 

Design  T.oad 
160  lb.  per  sq.  ft. 

St.  Louis  C 
380  lb.  per  sc 

L.  L. 

D.L. 

Total. 

L.L. 

D.  L. 

Total. 

Top  of  Slab  at 
Center 

Long  Span 
Short  Span 

402 
401 

100 
100 

100 
100 

200 
200 

675 
800 

100 
100 

775 
900 

Bottom  of  Slab  at 

Flange  of 
Supporting  Beam 

Lon 

Short 
Span 

*1Ci 
End 
Free 
End 

304 
801 

300 

325 
400 

160 

150 
200 

75 

475 
600 

225 

1,250 
1,525 

425 

150 
200 

75 

1.400 
1.725 

600 

Bottom  of  Slab  on 
Rib  just  outside 
of  Beam  Flange 

LOD 

Short 
Span 

End 
Free 
End 

308 
303 

311 

175 
400 

175 

75 
200 

100 

260 
600 

276 

926 
1.676 

700 

75 
200 

100 

1.000 
1,776 

800 

RsiNrORCElfENT 

AKD  Steel  Stbbsses. 

Location. 

Gauge 
Point. 

Design  T^d 
160  lb.  per  sq.  ft. 

St.  Louis  Code 
380  lb.  per  sq.ft. 

L.  L. 

D.L. 

Total. 

L.  L. 

D.L. 

Total. 

Bottom  of  Slab  at 
Center 

I>ong  Span 
Short  Span 

122 
113 

3,600 
7,500 

2,000 
3.600 

5,500  '  19,500 
11.000  ,  26,600 

2.000 
3.500 

21.500 
30,000 

Long  Span^ 

210 

3,600 

1.600 

6.000 

37,600 

1.600 

39.000 

Top  of  SUb  at 
Support 

Short 

l-ixea 
End 

201 

6.600 

3.600 

10,000 

28.600 

3.600 

32.000 

Span 

Free 
End 

219 

7.600 

4.000 

11.500 

8.600 

4.000 

12.600 

Short  Span 

101  & 
103 

7.000 

3.600 

10.600 

17,600 

3,600 

21.000 

Bottom  Flange  of 

Long 

Spandrel 
Beam 

128 

3.600 

2,000 

5,600 

9.500 

2.000 

11,600 

I  Beam 

Span 

Interior 
Beam 

124  & 
126 

7,600 

4,000 

11,600 

22.000 

4.000 

26.000 

load. 


Note. — Stresses  due  to  dead  load  are  obtained  by  projecting  the  stress  curve  to  the  soro 


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Report  of  Committee  on  Reinforced  Concrete.     157 

the  two  sets  of  ribs  can  be  reached  from  the  data  obtained  in  this 
one  testy  although  the  stresses  obtained  indicate  that  about 


nMBSSR^^^^^Sfl^^tSimrS^HIi^ 


FIQ.  73. — VARIATION  OF  STRESS  AND  LOCATION  OF  POINT  OF  INFLECTION  ALONG 
MIDDLE  BAR  IN  DIRECTION  OF  LONG  SPAN. 

65  per  cent  of  the  load  was  carried  across  the  short  span  of  the 
panel,  instead  of  the  55  per  cent  assumed. 


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DISCUSSION. 


Mr.  Ash.  Mr.  L.  R.  Ash. — I  would  like  to  know  if  experiments  have 

been  made  to  determine  whether  the  modulus  of  elasticity  of  high 
carbon  steel  is  really  more  than  that  of  medium  steel.  Some  claim 
that  high  carbon  steel  should  be  used  because  of  the  increased 
modulus  of  elasticity. 

One  other  question  is  whether  experiments  have  been  made 
to  determine  the  distribution  of  stresses  in  a  continuous  slab  with 
a  concentrated  load.  A  problem  that  frequently  comes  to  the 
bridge  designer  is  how  to  take  care  of  a  continuous  slab  which  has 
large  dimensions  one  way  and  small  dimensions  the  other,  for 
example  a  slab  supported  between  two  continuous  stringers. 

Mr.  Talbot.  Mr.  Arthur  N.   Talbot. — ^The  modulus  of  elasticity  of 

steel  is  a  fairly  definite  property.  It  varies  from  29,000,000  lb. 
per  sq.  in.  to  31,000,000,  perhaps;  the  average  of  tests  would 
bring  it  a  little  imder  30,000,000  lb.  per  sq.  in.  I  do  not  know 
that  anything  has  been  foimd  which  explains  or  gives  the  causes 
of  this  slight  variation.  I  am  quite  sure,  however,  from  tests 
which  we  have  made,  that  there  is  no  appreciable  difference 
in  the  modulus  of  elasticity  between  the  high  carbon  and  the  mild 
steel. 

It  is  an  important  question  to  determine  to  what  extent  it 
is  necessary  to  reinforce  a  slab  laterally  when  a  concentrated 
load  is  carried.  We  have  been  making  tests  along  this  line  at 
the  laboratory  of  the  University  of  Illinois  for  three  years  and  we 
hope  to  have  results  to  give  out  soon.  I  may  say  now  that  I 
have  been  surprised  to  find  how  little  reinforcement  is  necessary 
laterally  in  distributing  the  stresses  sidewise.  In  these  tests  we 
have  used  beams  30  and  48  in.  and  longer,  with  depths  of  4  to  7 
in.  and  with  widths  of  30  to  48  in.  These  slabs  were  loaded  in 
several  ways,  by  applying  the  load  entirely  across  the  beam,  by 
appljring  it  over  half  the  width  of  the  beam  and  also  over  1/5  of 
the  width  and  over  1/10  the  width.  In  a  general  way  it  may  be 
said  that  with  as  much  as  ^  of  one  per  cent  of  lateral  reinforcement 
the  stresses  are  distributed  laterally  over  a  width  of  say  8  or  10 
times  the  depth  of  the  beam. 

(168) 


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Report  of  Committee  on  Reinforced  Concrete.     159 

Mr.  W.  p.  ANDEBfiON. — In  making  the  comparison  with  the  Mr.  Andenon. 
bending  moments,  what  distance  was  used  for  the  span. 

Mr.  Talbot. — ^A  definite  length  had  to  be  assumed.    It  was  Mr.  xaibot. 
thought  best  to  use  something  more  than  the  clear  span  and 
3  in.  more  than  the  clear  span  for  both  girders  and  beams  was 
used.     This  is  somewhat  shorter  than  that  given  by  the  usual 
methods  of  design. 

Mr.  W.  K.  Hatt*  (By  Letter).— The  writer  has  read  this  Mr.Hmtt. 
important  contribution  with  a  great  deal  of  interest.  . 

It  is  realized  that  our  methods  of  computing  the  strength  of 
a  continuous  construction  of  slabs,  Boor  beams,  and  columns  of  a 
reinforced  concrete  building  is  conventional  and  very  largely 
empirical.  We  need  many  such  tests  as  are  described  in  this 
report  to  determine  the  allowable  limits  of  deflection  and  the  real 
factors  of  safety  obtaining  in  the  usual  designs.  The  common 
practice  of  loading  one  panel  is  evidently  misleading  since  sur- 
rounding panels  under  load  assist  in  carrying  the  load. 

The  report  confirms  the  opinion  many  have  had  that  under 
ordinary  working  loads  the  tensional  stresses  in  the  concrete 
assist  the  reinforcement  in  carrying  the  bending  moment  and  that 
the  conventional  computal  stress  of  16,000  lb.  will  not  be  found  in 
the  test  floor.  Of  course  imder  this  distribution  the  compressional 
stresses  will  be  the  critical  stresses. 

The  ratios  between  the  compressional  stresses  and  the  com- 
puted reinforcement  stresses  in  concrete  beams  reinforced  with 
various  percentages  of  metal  is  an  important  factor  in  the  work 
of  the  designer,  who  is  controlled  by  building  laws.  This  report 
does  not  comment  on  the  proper  values  of  this  ratio.  The  indica- 
tion from  the  tests,  however,  is  that  in  spite  of  high  compressional 
stresses  failiu-es  in  compression  are  not  evident.  The  recent  pub- 
lication of  the  Bureau  of  Standards  by  Messrs.  Richard  L.  Hum- 
phrey and  Louis  Losse,  fixes  an  extreme  fiber  stress  in  compression 
of  1000  lb.  per  sq.  in.  at  the  measured  unit  stress  of  16,000  lb.  per 
sq.  in.  in  the  reinforcement  for  1-2-4  concrete. 

The  writer  made  a  careful  test  of  the  Franks  building  in 
Chicago  in  the  siunmer  of  1911  and  submits  report  of  this  test 
as  a  contribution  to  the  discussion  of  this  subject. 


*PYofeflior  of  Civil  Engineeriiig,  Pardue  University.  Lafayette.  Ind. 


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160     Report  of  Committee  on  Reinforced  Concrete. 

REPORT  ON  TEST  FOR  ACTUAL  STRESSES  OF  THE 
A.  J.  FRANKS  BUILDING,  CHICAGO,  ILLINOIS. 

Bt  W.  K.  Hatt,  Consulting  Engineer,  Professor  of  Civil  Engineering, 
Purdue  University. 

During  the  latter  part  of  August,  1911,  the  undersigned  loaded  panels 
of  a  reinforced  concrete  building.  Fig.  1,  constructed  by  the  Leonard  Con- 
struction Company,  for  Mr.  A.  J.  Franks,  and  measured  the  actual  deforma- 
tions of  the  concrete  and  steel  under  load.  The  test  was  performed  upon  the 
basis  of  specifications  prepared  by  the  undersigned. 

In  brief,  the  panels  were  loaded  with  pig  iron  in  increments,  and  the 
accompanying  deformations  were  measured  in  the  steel  and  in  the  concrete 
at  all  critical  points,  with  a  view  to  fixing  a  safe  limit  of  loading  and  to  under- 
standing the  mechanical  action  of  the  structure. 

TEST  STRUCTURE. 

The  building  tested  is  a  ten-story  and  basement  warehouse  intended 
for  the  printing  and  paper  trades,  Dwight  Bros.  Paper  Company,  tenants. 
The  type  of  construction  used  was  the  Cantilever  Flat  Slab  System,  the  rein- 
forced concrete  setting  drawings  and  shop  details  being  made  by  the  Concrete 
Steel  Products  Company,  Engineers,  of  Chicago.  The  architects  of  the 
building  were  Richard  E.  Schmidt,  Garden  and  Martin.  The  design  load 
on  the  floors  was  taken  at  250  lb.  per  sq.  ft.  The  panel  dimensions  were 
19  ft.  4  in.  by  20  ft.  3  in.  The  four  panels  under  observation  were  in  the 
interior  of  the  building  and  on  the  tenth  floor  where  the  columns  were  of 
minimum  size.  As  the  effective  clear  span  between  capital  and  the  eccentric 
action  on  the  columns  were  the  greatest,  the  location  was  such  as  to  insure 
the  most  severe  test  possible. 

OBSERVERS  AND  METHODS  OF  OBSERVATION. 

The  observations  were  made  by  experienced  observers  as  follows:  Pro- 
fessor H.  H.  Scofield,  of  Purdue  University;  Professor  W.  A.  Slater,  of  the 
University  of  Illinois  Engineering  Experiment  Station;  Mr.  W.  E.  Ensign, 
of  the  University  of  Illinois  Engineering  Experiment  Station;  with  the  assist- 
ance of  Professor  L.  W.  Weeks,  of  Purdue  University. 

The  deformations  were  determined  by  the  use  of  extensometers  of  the 
type  devised  by  Professor  H.  C.  Berry  of  the  University  of  Pennsylvania. 
On  the  steel  a  gauge  length  of  10  in.  was  used,  which,  with  the  multiplying 
lever  in  the  instrument,  gave  direct  readings  of  unit  deformations  of  .00002 
in.  per  in.,  corresponding  to  stresses  of  600  lb.  per  sq.  in.  in  the  steel,  and 
it  was  possible  to  estimate  clearly  fractions  of  this  amount.  On  the  concrete 
readings  the  gauge  length  was  6  in.  and  the  direct  reading  of  unit  deforma- 
tions was  .000033,  corresponding  to  a  stress  of  133  lb.  per  sq.  in.,  and  it  was 
possible  to  estimate  fractions  of  this  amount  with  accuracy. 

Errors  in  operating  the  instrument  were  reduced  to  a  minimum  by  tak- 
ing every  reading  at  least  five  times  and  by  calibrating  on  a  standard  bar  at 


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Report  of  Committee  on  Reinforced  Concrete.     161 

frequent  intervals.  Four  standard  bars  were  used  throughout  the  test,  all 
of  these  being  embedded  in  the  concrete  and  subject  to  the  same  temperature 
changes  as  the  rods  in  the  test  floor  but  free  from  any  stress  due  to  applied 
load.     By  reading  on  these  bars  between  sets  of  five  or  six  test  readings  the 


FIG.   1. — A.  J.   FRANKS  BUILDINQ  IN  COURSE  OF  CONSTRUCTION, 
CHICAGO,  ILL. 

observations  on  the  materials  under  test  were  freed  from  temperature  differ- 
ences and  systematic  errors. 

The  deflections  were  measured  to  .0001  in.  by  use  of  the  deflectometer 
described  in  a  previous  test  fQr  actual  stresses. 


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162     Repobt  of  Committee  on  Reinforced  Concrete. 

Tensile  defonnations  were  measured  throughout  the  test  over  42  gauge 
lengths  on  the  steel  reinforcing  rods;  compressive  deformations  in  the  con- 
crete were  measured  over  26  gauge  lengths;  deflections  were  observed  at  24 
points,  and  27  other  readings  of  deformations  were  taken  throughout  the  test 
to  study  such  phenomena  as  the  arch  and  slab  action,  the  distribution  of 


FIQ.  2. — ^LOCATION  OF  GAUGE  LBNGTHS  IN  CONCRBTB  BLAB. 

stress,  and  the  eccentric  loading  on  the  columns  at  the  edges  of  the  loaded 
area.    The  location  of  the  gauge  lengths  is  given  in  Figs.  2  and  3. 

The  observations  were  arranged  in  groups,  each  designed  to  cover 
adequately  some  particular  feature,  and  synmietrically  located  observations 
were  obtained  as  a  check  in  every  case  where  possible,  in  order  to  cover  varia- 
tions in  the  quality  of  the  concrete  at  different  points. 


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Report  of  CoMBflTTEE  on  Reinforced  Concrete.     163 

The  conditions  were  exceptionally  favorable  to  a  satisfactory  test. 
The  building  was  practically  completed  at  the  time  of  test  and  the  variation 
in  temperature  was  very  slight,  being  about  74**  at  the  start  of  the  test, 
dropping  gradually  and  uniformly  to  70°,  and  rising  again  at  the  end  to  74°. 


FIG.  3. — LOCATION  OF  GAUGE  LENGTHS  IN  REINFORCING  RODS. 

The  slab  was  poured  on  June  23, 1911,  and  was  64  days  old  when  the  maximum 
load  of  624  lb.  per  sq.  ft.  of  panel  area  was  placed  upon  it. 

LOADING. 

The  amount  of  loading  was  determined  by  the  weight  of  the  pig  iron  as 
recorded  on  the  weigh  bills  delivered  by  the  teamsters,  and  was  checked  by 
weighing  a  number  of  piles  of  pig  iron  from  the  test  load  on  a  platform  scales. 

The  pig  iron  was  piled  on  the  floor  in  separate  piers,  Fig.  4,  each  placed 


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Report  of  Committee  on  Reinforced  Concrete.     165 

within  a  two-foot  square,  so  that  no  arch  action  existed  in  the  load  itself  to 
relieve  the  panel  from  moment.  It  was  necessary  to  leave  several  of  these 
squares  vacant  about  columns  and  to  leave  an  aisle  between  the  columns  to 
allow  space  for  observations.  The  pig  iron  belonging  on  these  vacant  squares 
was  distributed  over  the  remaining  squares  of  the  same  panel.  It  will  be 
apparent  that  under  this  procedure  the  real  load  intensity,  as  affecting  bend- 
ing stresses  and  deflections,  is  the  intensity  of  loading  over  the  loaded  area 
(about  90  per  cent  of  panel  area),  rather  than  the  nominal  or  average  load 
over  the  entire  panel  area.  It  is  evident  that  had  the  10  per  cent  of  panel 
area  close  to  the  columns  been  loaded  to  the  same  intensity  the  increase  in 
stresses  and  deflection  would  have  been  practically  nil. 

All  gauge  lengths  were  measured  and  checked  throughout  before  loading 
was  started.  When  the  loading  reached  certain  amounts,  distributed  evenly 
over  four  panels,  it  was  discontinued  and  allowed  to  stand  for  6  hours  before 
the  observations  were  made  and  the  loading  resumed.  The  increments  of 
load  at  which  measurements  were  made  were  as  follows:  75,  150,  256  (the 
design  load),  312  (intensity,  359),  and  624  (intensity,  717)  lb.  per  sq.  ft., 
the  latter  load  being  applied  to  two  panels  only.  Readings  were  also  taken 
with  256  on  two  diagonal  panels  and  312  on  the  other  two  panels,  and  with 
468  on  two  diagonal  panels  and  156  on  the  others,  but  without  waiting  for 
the  six-hour  interval  to  elapse  before  taking  readings.  The  total  number 
of  complete  observations  over  single  gauge  lengths  was  over  2,000,  and  the 
total  individual  readings  over  10,000. 

STRESSES. 

The  stresses  were  determined  from  the  observed  deformations  by  using 
a  modulus  of  elasticity  of  30,000,000  lb.  per  sq.  in.  for  the  steel,  and  4,000,000 
lb.  per  sq.  in.  for  the  concrete.  The  latter  value  was  determined  from  tests 
of  three  concrete  prisms  poured  from  the  concrete  in  the  test  slab  and  tested 
at  Purdue  University  at  an  age  of  77  days. 

Table  I  gives  a  summary  of  the  corrected  values  of  the  total  dead  and 
live  load  stresses  observed  in  the  various  groups  of  observations.  The  detailed 
summary  of  individual  stresses  at  the  various  observation  points  are  omitted 
in  this  report.  After  the  observations  had  been  corrected  for  temperature 
and  observational  errors,  by  use  of  the  standard  bar  calibrations,  load  deforma- 
tion curves  were  plotted  for  each  observation  point,  the  known  nature  of  the 
load  deformation  curve  under  flexure  being  used  as  a  basis.  The  dead  load 
stress  has  been  taken  from  these  curves  as  equal  to  the  stress  caused  by  an 
equal  live  load. 

COMMENTS  ON  THE  RESULTS. 

The  undersigned  is  not  prepared  at  the  present  time  to  state  the  signifi- 
cance of  the  results  obtained  with  respect  to  the  mechanics  of  this  form  of 
construction.  Such  statements  would  have  somewhat  of  a  speculative  ele- 
ment and  should  be  separated  from  the  report  of  test  which  is  one  of  measured 
facts. 


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166     Report  of  Committeb  on  Rbinfobced  Concrete. 

As  compared  with  the  design  requirements  of  the  Chicago  Building 
Code,  it  is  interesting  to  note  that  at  design  load  the  highest  average  stress 
in  the  steel  is  5078  lb.  per  sq.  in.,  while  the  highest  average  compressive 


.ft. 


Table  I. — Condensed  Summary  of  Actual  Stresses. 

All  stresses  are  the  final  values  for  total  dead  and  live  load,  and  are  given 
in  lb.  per  sq.  in. 

Stresses  in  Slab  Rods. 

oJt^JSS.tc.,  DeBcription.  ^3^ 

5,  6,  7,  14,  15,  16 Center  of  span,  diagonal  band  1071 

8,  9,  10,  11,  12,  13 Center  of  span,  cross  band  . .  4539 

31,32,33,34,35,37 Over    capital    at    center  col- 
umn, diagonal  band 3440 

27,  28,  29,  30 Over  capital    at    center    col- 
umn, cross  band 4575 

21,22,23 Over  capital    at    comer    col- 
umn, diagonal  band 1920 

24,  25,  26,  41,  42,  43 Over  capital  at  side  column, 

cross  band 2690 


Live  Load-lb.  per  0q.  f 
812    624 

1920 

6140 


10095 


4350  9280 

4840  8140 

2280  7540 

3138  5315 


Compressive  Stresses  in  Concrete. 
66,  67,  69,  60,  68,  69,  70.  .On  slab  at  center  column. .    . 

61,  62,  65,  66 On  drop  at  center  column. . . 

61,  74 On  drop  at  comer  column . . . 

52,  53,  73 On  slab  at  corner  column .... 

54,  55,  71,  72 On  slab  at  side  columns   


560  650  1206 

677  778  1685 

318  370  1515 

329  378  650 

189  217  420 


Mcudmum  Stresses  in  Columns  Due  to  Eccentric  Live  Load. 

104 . .  Compression  in  concrete,  corner  column 680      840  1660 

109.  .Compression  in  concrete,  side  column 416      512  1000 

84.  .Tension  in  steel,  comer  column 4980    6000  11620 

99.  .Tension  in  steel,  side  column   2220    2640  5880 


Deflections  in  Inches. 

121,  124.  .Center  of  panel— at   6  hours 123 

Center  of  panel — at  24  hours 

After  standing  unloaded  6  hours 142 

After  standing  unloaded  2)  days 090 


.156 


.475 
.500 


stress  in  the  concrete  is  677  lb.  per  sq.  in.  On  the  basis  of  safe  working 
stress  in  the  steel  of  16,000  lb.  per  sq.  in.,  and  in  the  concrete  of  35  per 
cent  of  the  ultimate  strength  (which  averaged  over  3250  by  tests  of  prisms) 
or  1100  lb.  per  sq.  in.;   it  appears  that  the  steel  is  stressed  to  31  per  cent 


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Report  op  Committee  on  Reinforced  Concrete.     167 

of  its  safe  load  while  the  concrete  is  stressed  to  62  per  cent  of  its  safe  load. 
It  appears,  therefore,  that  the  design  is  overbalanced  with  an  excess  of  steel. 
At  the  highest  applied  load  of  717  lb.  per  sq.  ft.,  the  ratio  of  the  steel  and 
concrete  stresses  remains  practically  unchanged. 

The  eccentric  action  of  the  test  load  was  most  marked  on  the  comer 
columns  of  the  loaded  area  and  was  suj£cient  to  produce  a  tension  in  the 
steel  of  5000  lb.  per  sq.  in. 

With  respect  to  the  strength  of  the  structure,  it  may  be  said  that  a  nominal 
load  of  624  lb.  per  sq.  ft.  of  panel,  actually  717  lb.  per  sq.  ft.  of  loaded  surface, 
was  applied  without  producing  any  permanent  damage  to  the  building.  At 
this  load  the  highest  observed  average  total  dead  and  live  load  stresses  were 
less  than  12,000  lb.  per  sq.  in.  in  the  steel  and  less  than  1700  lb.  per  sq.  in. 
on  the  concrete. 

From  a  consideration  of  the  data  from  the  above  test  the  writer  con- 
cludes that  the  A.  J.  Franks  Building  is  amply  strong  to  carry  the  designed 
load  and  that  the  lower  floors  at  least  may  safely  and  continuously  be  loaded 
with  considerably  more  than  the  designed  load. 

(Signed)  W.  K.  Hatt. 


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THE  TESTING  OF  REINFORCED   CONCRETE 
BUILDINGS  UNDER  LOAD. 

By  W.  A.  Slater.* 

I.    Introduction. 

Development  of  Building  Tests. — ^For  several  years  there  has 
been  a  growing  demand  for  tests  of  full-size  structural  members. 
A  more  recent  development  is  the  test  of  structures  themselves 
and  the  measurement  of  actual  stresses  in  the  component  parts. 

Load  tests  have  been  required  by  city  building  departments 
as  a  condition  of  acceptance  of  reinforced  concrete  buildings  and 
have  been  used  by  construction  companies  and  engineers  to 
demonstrate  the  adequacy  of  various  designs.  Such  load  tests 
are  never  continued  to  destruction,  the  applied  load  being  gen- 
erally twice  the  design  live  load,  and  emphasis  is  placed  upon 
measurement  of  deflection  and  recovery.  No  measurements  of 
stresses  are  made  in  such  tests  and  under  these  conditions  the 
safe  load  can  not  be  fixed  upon  as  a  definite  ratio  of  the  ultimate 
load.  The  deflections  observed  in  such  tests  constitute  a  very 
inadequate  and  actually  misleading  measure  of  the  stresses. 
Slight  deflections  have  been  taken  to  indicate  low  stresses  in 
reinforcement  and  in  concrete,  but  recent  tests  in  which  deforma- 
tions were  measured  have  shown  that  even  with  slight  deflections 
large  stresses  are  developed  in  concrete  even  when  the  reinforce- 
ment stresses  are  low.  The  tendency  of  building  codes  was  to 
disregard  continuity  of  action  in  beams  in  reinforced  concrete 
buildings  and  to  specify  the  design  as  of  simple  beams,  but  even 
in  such  cases  a  small  amount  of  reinforcement  was  placed  across 
the  support  to  prevent  the  opening  of  large  cracks.  This  rein- 
forcement and  the  tensile  strength  of  the  concrete  have  been 
sufficient  to  develop  a  large  stress  in  the  concrete  at  the  support 
which  may  not  have  been  specifically  provided  for.  Thus  the 
so-called  conservative  attitude  of  not  allowing  anything  for 
continuity  of  beams  at  the  support  may  prove  a  source  of  weak- 

*  Engineering  Experiment  Station,  University  of  Illinois.  Urbana.  111. 

(168) 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    169 


The  measurements  of  deformations  in  building  structures 
eonfirms  the  truth  of  this  statement. 

Purpose  and  Scope  of  this  Paper. — ^The  reports  of  all  building 
tests  in  which  deformations  have  been  measured  deal  in  the  main 
with  the  behavior  of  the  structure  and  record  the  results,  and  are 
not  primarily  concerned  with  the  working  of  the  instruments  or 
with  the  methods  of  making  the  tests.  To  conduct  a  successful 
building  test  is  diflScult,  however,  and  this  paper  is  written  in 
order  to  present  information  as  to  methods  of  testing  gained  by 
experience  and  to  point  out  certain  respects  in  which  such  tests 


1 


Building 


euf'Mhff 


CorMfon  Bolklfng 


•RELATIVE  SIZE  OF  FLOOR  AREAS  TESTED. 


may  be  conducted  more  satisfactorily  than  those  which  have 
already  been  made.  The  following  general  order  of  presenting 
the  material  in  hand  will  be  observed:  (1)  enumeration  of  tests, 
(2)  the  planning  and  preparation  for  a  test,  (3)  the  instruments; 
their  construction  and  use,  and  the  methods  of  making  observa- 
tions, (4)  the  methods  of  making  calculations  and  (5)  the  cost  of 
a  test. 

The  following  is  a  list  of  tests  of  building  floors  in  which  the 
methods  described  herein  of  measuring  deformation  were  used. 
Fig.  1  shows  the  range  in  size  of  these  test  areas. 


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170    Slater  on  Testing  Reinforced  Concrete  Buildings. 

Test  No.  1. — Deere  and  Webber  Building,  Minneapolis, 
Minnesota,  October  and  November,  1910;  flat  slab  floor  with 
four-way  reinforcement;  built  by  Leonard  Construction  Com- 
pany of  Chicago,  and  tested  by  them  with  the  co-operation  of 
the  Erigineering  Experiment  Station  of  the  University  of  Illinois. 

Test  No.  2. — ^Wenalden  Building,  Chicago,  Illinois,  June  and 
July,  1911.  Beam  and  girder  building  constructed  by  Ferro- 
concrete Construction  Company  of  Cincinnati,  and  tests  made 
by  co-operation  between  the  National  Association  of  Cement 
Users,  the  Ferro-Concrete  Construction  Company  and  the  Engi- 
neering Experiment  Station  of  the  University  of  Illinois. 

Test  No.  3. — ^The  Powers  Building,  Minneapolis,  Minnesota, 
July  and  August,  1911;  flat  slab  floor  with  two-way  reinforcement; 
built  and  tested  by  Corrugated  Bar  Company  of  St.  Louis. 

Test  No.  4. — ^Franks  Building,  Chicago,  Illinois,  August, 
1911;  flat  slab  floor  with  four-way  reinforcement;  buUt  and 
tested  by  Leonard  Construction  Company  of  Chicago. 

Test  No.  5. — ^Turner-Carter  Building,  Brooklyn,  New  York, 
September,  1911;  beam  and  girder  floor;  built  by  Turner  Con- 
struction Company  of  New  York;  test  made  by  co-operation 
between  National  Association  of  Cement  Users,  the  Turner 
Construction  Company  and  the  Engineering  Experiment  Station 
of  the  University  of  Illinois. 

Test  No.  6. — Carleton  Building,  St.  Louis,  Missouri,  October, 
1911;  flat  slab  floor  with  two-way  reinforcement;  built  and 
tested  by  Corrugated  Bar  Company. 

Test  No.  7. — ^Barr  Building,  St.  Louis,  Missouri,  December, 
1911;  full  size  test  panel  (25  ft.  x  26  ft.  9  in.).  Terra-cotta  tile 
used  to  lighten  construction;  gives  two-way  T-beams  with  web 
between  tile  on  tension  side  and  concrete  flange  above  the  tile; 
two-way  reinforcement.  Panel  built  by  Corrugated  Bar  Com- 
pany to  demonstrate  eflSciency  of  design  proposed  for  Barr  Build- 
ing in  St.  Louis;  test  made  by  Corrugated  Bar  Company. 

Test  No.  8. — Ford  Motor  Building,  Detroit,  Michigan, 
February  and  March,  1912;  flat  slab  floor;  built  and  tested  by 
the  Corrugated  Bar  Company. 

These  seem  to  be  the  only  full-size  reinforced  concrete  floor 
tests  on  record  in  which  deformations  in  reinforcement  and  con- 
crete have  been  measured.     The  writer  was  in  immediate  charge 


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Slater  on  Testing  Reinforced  Concrhtb  Buildings.    171 

of  Tests  Nos.  2  and  5  and  had  a  part  in  tlie  conduct  of 'all  "tjie 
others  except  Tests  Nos.  6  and  8.  I'jie  'motfioas'  of  t&3tiag 
presented  in  this  paper  were  developed  by  the  writer  as  a ,  result 
of  his  connection  with  the  tests.  These  meth'ods*v>^re  ji^dft^^'V^ 
increase  the  accuracy  of  results,  to  avoid  accidental^  errors^  ai».d  t^ 
correct  for  systematic  errors. 

Much  credit  for  the  initiative  in  this  type  of  test  ife  due  Mr. 
A.  R.  Lord,  formerly  research  fellow  at  the  University  of  Illinois, 
who  was  largely  instrumental  in  bringing  about  the  test  of  the 
Deere  and  Webber  Building,  the  first  in  the  series  named.  After 
the  presentation  of  Mr.  Lord's  paper  on  the  test  of  the  Deere  and 
Webber  Building,  The  National  Association  of  Cement  Users 
decided  to  continue  the  investigation.  All  of  the  tests  given  in  the 
above  list  were  conducted  on  the  same  general  lines  as  that  of  the 
Deere  and  Webber  Building.  Only  the  tests  of  the  Wenalden 
Building  and  the  Turner-Carter  Building  were  in  the  series  author- 
ized by  the  National  Association  of  Cement  Users,  but  the  results 
of  the  tests  made  by  the  Corrugated  Bar  Company  on  the  Powers 
Building  and  on  the  Barr  Building  test  panel  have  been  placed 
at  the  disposal  of  the  Association.  The  Franks  Building  test, 
made  by  the  Leonard  Construction  Company,  was  an  investigation 
planned  to  give  data  for  an  intelligent  modification  of  the  Chicago 
Building  Code.  The  other  two  tests,  those  of  the  Carleton  Build- 
ing and  the  Ford  Motor  Building,  were  in  the  nature  of  investiga- 
tion of  special  features  of  design.  The  methods  used  in  all  of 
these  tests  are  essentially  the  same  and  have  been  developed 
at  the  University  of  Illinois  Engineering  Experiment  Station. 

Available  Literature, — Reports  of  results  of  some  of  these 
tests  are  available  as  follows: 

1.  Deere  and  Webber  Building. 

Paper  by  A.  R.  Lord,  "A  Test  of  a  Flat  Slab  Floor  in  a 
Reinforced  Concrete  Building."  ProceedingSf  Vol.  VII, 
1911. 

Abstracts:  Engineering  News,  December  22,  1910;  Engi- 
neering-Contracting, December  22,  1910. 

2.  Wenalden  Building  and  Turner-Carter  Building. 
Report  of  Committee  on  Reinforced  Concrete  and  Build- 
ing Laws,  Part  I.    Proceedings,  Vol.  VIII,  1912.* 


♦See  pp.  61-167.— Ed. 


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172   Slater  on  Testing  Reinforced  Concrete  Buildings. 


•  •  •  •  • 


•  ••  •' 


Abilrkctfi  f  \Fngin6efi7iy.  i?6cord,  March  23  and  April  13, 
•  le/^y  i^inf  4r«W  Vf  ^w's,  April  18,  1912;    and  CetnerU 

••\i: : .. .  :-4ffV^ei;w  *•* 

•/  ;  S?*!  JVveiiHuiiaihg  and  Barr  Building  Test  Panel. 
.  .  .'.  *.  *.llep6y;  g/  tlgmi^ttee  on  Reinforced  Concrete  and  Building 
;:  V:  (  }  V  Law)a;-i^arteil  and  III.    Proceedings,  Vol.  VIII,  1912.* 
Abstracts:    Engineering  News,  April  18,  1912;  and  Engi- 
neering  Record,  April  20, 1912. 
4.  Franks  Building. 

(a)  Abstracts  of  paper  by  W.  K.  Hattf  before  Indiana 
Engineering  Society,  Engineering-Contracting,  March 
13,  1912;  and  Engineering  News,  April  8,  1912. 
(6)  Discussion  by  W.  K.  Hatt  on  Report  of  Committee  on 
Reinforced  Concrete  and  Building  Laws,  Proceed- 
ings, Vol.  VIII,  1912.t 
(c)  Trade  publication  on  Cantilever  Slabs  published  by 
Concrete  Steel  Products  Company,  Chicago,  111. 

II.    Conduct  op  Tests. 

DEFINITIONS. 

In  the  following  descriptions  of  tests,  many  terms  will  be 
used  for  which  somewhat  arbitrary  definitions  will  need  to  be  made. 
These  definitions  are: 

Gauge  Hole:  A  small  hole  (.055  in.  is  here  recommended) 
drilled  into  the  steel  bar  or  into  the  plug  inserted  in  the  concrete 
has  been  termed  a  gauge  hole.  It  is  for  the  admission  of  the  point 
of  a  leg  of  the  extensometer. 

Gauge  Line:  The  gauged  length  connecting  a  pair  of  gauge 
holes  is  termed  a  gauge  line. 

Reading:  A  reading  is  a  single  observation  on  any  gauge  line. 

Observation:  An  observation  as  here  used  is  the  average  of  a 
number  of  readings. 

Zero  Length  of  Instrument:  The  length  of  the  instrument  at 
the  time  of  taking  the  first  observation  on  the  standard  bar  will 
be  known  as  the  zero  length  of  tlie  instrument.    This  first  observa- 


•  See  pp.  61-157.— Ed. 
t  See  pp.  159-167.— Ed. 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    173 

tion  on  the  standard  bar  is  not  the  zero  length,  but  a  comparison 
of  a  subsequent  observation  with  it  shows  any  change  from  the 
zero  length. 

Correction:  A  correction  is  the  amount  which  if  added  alge- 
braically to  the  observation  will  give  the  observation  which  would 
have  been  obtained  if  the  instrument  had  not  changed  from  its 
zero  length. 

Series  of  Observaiiona:  The  observations  taken  consecutively 
at  a  given  load  without  repetitions  on  any  gauge  line  ar^  defined  as 
a  series  of  observations. 

Interval:  An  interval  as  used  here  is  the  time  elapsing  between 
consecutive  observations,  and  all  intervals  in  *any  series  are  (for 
lack  of  more  exact  information)  assumed  to  be  equal.  For  this 
piupose  the  average  of  two  consecutive  observations  on  standard 
gauge  lines  is  considered  a  single  observation. 

Standard  Gauge  Line:  This  is  a  gauge  line  used  usually  to 
determine  changes  of  length  of  instrument,  of  reinforcement  or  of 
concrete  due  to  other  causes  than  the  applied  load.  Its  purpose 
usually  is  to  determine  the  temperature  effect  on  the  instrument, 
but  it  may  be  used  to  detect  accidental  changes  of  instrument  or 
temperature  stresses  in  the  reinforcement  of  the  concrete.  Origi- 
nally this  gauge  line  was  placed  on  a  steel  bar  separate  from  the 
structure,  and  this  gave  rise  to  the  term  standard  bar.  In  several 
of  the  later  tests,  however,  the  standards  have  consisted  of  gauge 
lines  placed  in  the  reinforcement  and  concrete  of  the  structure 
remote  from  the  area  affected  by  the  load.  Standard  gauge  line 
is  adopted,  therefore,  as  the  more  general  term  and  any  reference 
to  the  standard  bar  may  be  understood  to  signify  the  standard 
gauge  line  on  a  bar  separate  from  the  structure. 

general  outline  of  method  of  testing. 

After  determining  what  measurements  will  best  give  the 
information  desired  from  the  test,  the  gauge  lines  are  laid  off  on' 
the  surface  of  the  concrete  and  small  holes  are  cut  or  drilled  in  the 
concrete  at  a  predetermined  distance  apart  in  order  to  expose  the 
reinforcement  or  allow  a  metal  plug  to  be  inserted,  according  as 
the  measurement  is  of  reinforcement  or  concrete  deformation. 
The  metal  plugs  used  are  securely  held  in  place  by  imbedment' 


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174    Slater  on  Testing  Reinforced  Concrete  Buildings. 

in  plaster  of  Paris.  The  gauge  holes  having  been  carefully  pre- 
pared;  a  set  of  zero  readings  is  taken  on  all  gauge  lines,  an  increment 
of  the  loading  material  is  then  added  and  a  second  series  of  observa- 
tions on  the  gauge  lines  taken.  The  difference  between  the  two 
readings  on  the  same  gauge  line  represents  the  deformation  in 
that  gauge  line.  It  is  possible  that  this  apparent  deformation 
may  be  due  partly  to  temperature  changes  in  the  instrument 
instead  of  stress  changes  of  the  material  by  reason  of  applied  load. 
For  this  reason  reference  measurements  are  made  on  standard 
unstressed  bars  made  of  Invar  steel  which  has  a  very  low  coefficient 
of  expansion  and  whose  change  in  length  due  to  temperature 
would  therefore  bfe  very  sUght.  From  these  readings  on  the 
standard  bar,  temperature  corrections  are  computed  as  shown  in  a 
later  paragraph  and  applied  to  the  observations  in  order  to  deter- 
mine the  actual  change  in  length  of  the  gauge  line.  Another 
increment  of  load  is  then  applied  and  another  series  of  observations 
taken. 

Floor  deflections  also  have  been  measured  in  all  of  these  tests, 
but  they  have  been  considered  as  of  secondary  importance.  They 
have  been  used  to  throw  light  on  the  correctness  or  incorrectness 
of  the  deformation  readings  and  to  gain  some  idea  of  the  general 
distribution  of  stresses  throughout  a  floor.  They  can  apparently 
be  depended  upon  to  show  with  considerable  accuracy  the  pro- 
portional rate  of  increase  of  stress,  but  deflection  formulas  are  so 
imperfect  that  measurement  of  deflections  can  not  be  depended 
upon  to  give  the  actual  values  of  stresses. 

Measurements  of  dimensions  such  as  span,  depth  of  beams, 
location  of  observation  points,  weight  of  loading  material,  location 
of  cracks,  and  any  other  measurements  which  were  considered  of 
value  in  working  up  results  have  been  carefully  taken.  The 
measurements  taken  are  usually  distributed  over  and  under  the 
surface  of  the  floor  tested  in  order  to  gain  an  idea  of  the  changes 
occiuring  in  different  parts  of  the  structure. 

The  above  statement  gives  in  general  terms  the  features  of 
any  one  of  the  tests  dealt  with  in  this  paper.  There  are  many 
difficulties  to  overcome  and  many  chances  for  error.  What 
follows  is  concerned  mainly  with  the  method  of  overcoming  these 
difficulties  and  avoiding  these  errors.  Most  of  the  statements 
made  represent  the  results  of  experience  on  previous  building 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    175 

tests.     Some  merely  give  ideas  which  it  is  believed  if  put  into 
operation  would  be  advantageous. 

the  planning  op  a  test. 

Each  test  made  will  involve  individual  consideration  of  the 
choice  of  area  to  be  loaded,  the  number  and  location  of  gauge 
lines  and  deflection  points,  the  number  of  laborers  required,  the 
loading  material  to  be  used  and  its  distribution,  and  provisions 
for  storage  of  the  loading  material  near  the  test  area  without 
appreciably  affecting  the  stresses  which  are  to  be  measured. 
Other  matters  will  come  up  for  consideration,  but  in  the  main 
they  will  not  require  different  solutions  for  each  test. 

Choice  of  Test  Area. — The  area  to  be  loaded  should  be  chosen 
so  as  to  fulfil  the  following  conditions  as  completely  as  possible: 

(a)  It  should  be  so  located  as  to  give  conditions  in  the  beams, 
slabs,  columns,  etc.,  as  severe  as  will  be  found  anywhere  in  the 
building  when  in  use. 

(6)  It  should  be  free  from  irregularities  of  construction. 

(c)  It  should  be  as  free  as  possible  from  disturbances  of 
workmen. 

(d)  It  should  be  as  easily  accessible  to  the  loading  material 
as  possible. 

In  most  cases  some  limitation  is  found  on  part  or  all  of  the 
conditions  named.  For  example,  in  the  test  of  the  Wenalden 
Building  it  was  impossible  to  find  an  area  entirely  free  from  irregu- 
larities of  construction.  An  industrial  track  crossed  one  of  the 
panels  chosen,  and  the  floor  was  thicker  immediately  under  this 
track  than  at  other  places.  On  the  edge  of  one  or  two  of  the  panels 
tested,  beams  about  an  inch  deeper  than  the  regular  beams  were 
located.  However,  none  of  the  measurements  assumed  to  give 
typical  results  were  taken  in  these  panels,  and  it  is  believed  that 
the  stresses  in  the  other  panels  were  not  affected  appreciably  by 
these  irregularities.  Again,  in  the  test  of  the  Franks  Building 
it  was  not  possible  to  choose  a  lower  floor  convenient  to  the  loading 
material.  An  upper  floor  was  used  in  order,  during  the  course  of 
construction,  to  make  preparation  for  the  test,  thus  avoiding  dig- 
ging in  the  concrete.  However,  this  choice  of  a  floor  fulfilled  one 
of  the  conditions  mentioned,  in  that  it  gave  a  much  more  severe 
test  of  the  columns  than  a  test  on  a  lower  floor  would  have  done. 


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176    Slater  on  Testing  Reinforced  Concrete  Buildinqs. 

Also,  in  the  test  of  the  Carleton  Building  at  St.  Louis  the  area  to 
be  tested  was  specified  by  the  city  building  department,  and  there 
was  no  choice  as  to  location  on  the  part  of  those  making  the  test. 
Number  oj  Measurements. — ^The  number  of  measurements  to 
be  taken  will  depend  upon  the  nature  of  the  test,  the  number  of 
observers,  and  the  number  of  laborers.  If  the  test  is  a  part  of  a 
series  by  which  it  is  expected  to  gain  scientific  information  which 
will  afford  a  basis  for  design,  it  is  likely  that  it  will  be  deliberate 
enough  that  a  large  number  of  measurements  may  be  taken. 
Such  tests  were  those  of  the  Wenalden  Building,  the  Franks 
Building,  the  Turner-Carter  Building,  and  the  Barr  »test  panel. 


Pl/^n5how/a4  5  Location     ^  1    >  f>L/9AfSMO¥Y*MgLoCATtON 

o^  fio/Afrs  OAf   Top  OF  Slab    "^y^        or  Po/Afrs  cr^Sorromor  Sl^B 

••  M[>inf  on  sfevi  ' 

0aQg0l9nff/i  8  tnc/»99  I 

FIG.  2. — ^LOCATION  OF  GAUGE  POINTS,   CARLETON  BUILDING. 

If,  on  the  other  hand,  the  test  has  more  of  a  commercial 
nature  or  is  a  utilization  of  the  opportunity  offered  by  the  accept- 
ance test  to  take  some  measurements  which  will  show  actual 
stresses,  or  if  for  any  other  reason  the  test  is  hurried,  the  number 
of  measurements  will  necessarily  be  rather  small.  Of  this  class, 
the  tests  of  the  Carleton  Building  in  St.  Louis  and  of  the  Ford 
Motor  Building  in  Detroit,  Michigan,  are  good  examples.  Notice 
was  given  the  engineers  only  about  one  day  in  advance  that  a 
test  would  be  made  on  the  Carleton  Building.  Permission  was 
obtained  from  the  contractor  to  expose  bars  for  measurement  in 
various  points  and  to  erect  the  necessary  scaffolding.    The  meas- 


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Slater  on  Testing  Reinforced  Concrete  BxnLDiNGs.     177 

urements  were  made  more  for  the  purpose  of  checking  the  anal- 
ysis upon  which  the  design  was  based  than  to  form  in  itself  a 
basis  of  design.  Therefore  comparatively  few  observation  points 
were  used.  It  is  believed  that  this  test  is  representative  of  the 
type  of  test  which  is  practicable  on  a  commercial  basis,  hence  (by 
courtesy  of  the  Corrugated  Bar  Company)  a  plan  is  given  in 
Fig.  2  showing  the  points  where  measurements  were  taken. 

Disirihulwn  of  Measurements. — The  arrangement  of  observa- 
tion points  will  depend  on  what  are  the  principal  subjects  for 
investigation  in  the  test.  Whatever  the  subject  of  study  may  be, 
the  observation  points  should  be  arranged  in  such  a  way  that  a 
curve  of  deformations  may  be  plotted  against  distance,  showing 


I  ^  5  S  § 
§  §  §  §  § 


§  ^  S  ^  § 


^  S  S 


Deformat/on  per  Unit  of  Length. 

PIG.   3. — LOAD-DEFORMATION  DIAGRAM  FOR  SERIES  OP  GAUGE  LINES  ON 
REINFORCEMENT,    POWERS*  BUILDING. 

a  gradual  progression  from  the  condition  at  one  part  of  the  struc- 
ture to  the  condition  at  another,  for  it  is  found  that  there  are  even 
imder  the  most  careful  work,  inconsistencies  which  will  make  the 
results  look  doubtful  if  standing  by  themselves.  The  points  so 
arranged  should  be  numerous  near  the  place  where  the  measure- 
ments of  greatest  importance  are  to  be  taken,  so  that  the  results 
will  not  depend  upon  measurements  at  a  single  point,  or  upon  the 
average  at  portions  of  the  structure  supposed  to  be  similarly 
situated  but  in  different  parts  of  the  building  where  unknown 
conditions  may  actually  cause  a  large  variation  in  the  phenomena 
of  the  test.  It  will  not  be  possible  to  carry  out  this  plan  for  all 
subjects  of  investigation,  as  the  number  of  observations  required 


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178    Slater  on  Testing  Reinforced  Concrete  Buildings. 

would  usually  be  impracticably  large.  Such  provisions  may  be 
made  to  cover  the  main  lines  of  investigation,  and  isolated  obser- 
vation points  may  be  used  to  gain  information  as  to  tendencies 
of  other  portions  of  the  structure,  but  of  course,  less  reliance  must 
be  placed  on  the  results  of  the  latter  measurements  than  where 
the  larger  number  of  observations  is  made.  It  would  be  advan- 
tageous, as  was  done  in  the  Powers  Building  test  and  also  in  the 
Barr  test  panel,  for  two  observers  to  check  measurements  on  the 


FIG.  4. — LOCATION  OF  GAUGE  LINES,   POWERS  BUILDING. 

same  points.     One  or  both  of  these  checks  is  very  valuable  in 
establishing  the  correctness  of  observations. 

Figs.  3,  4,  5,  and  6  illustrate  the  former  method.  Fig.  3  gives 
the  load  deformation  diagrams  for  several  gauge  lines  in  the  test 
of  the  Powers  Building.  Fig.  4  shows  the  location  of  these  points 
with  reference  to  the  wall  and  a  column.  Fig.  5  shows  the  same 
data  plotted  as  deformation  against  distance  from  the  column 
instead  of  against  load.  It  may  be  seen  that  the  correctness  of 
the  load  deformation  curve  for  one  of  these  points,  if  standing  by 


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Slateb  on  Testing  Reinforced  Concrete  Buildings.    179 

itself,  might  be  doubted  because  of  the  complete  change  in  the 
character  of  the  curve  at  a  load  of  200  lb.  per  sq.  ft.  But  when 
these  deformations  are  plotted  against  distance,  the  results  look 
so  consistent  that  it  is  scarcely  conceivable  that  they  are  seriously 
incorrect.  In  the  test  of  the  Wenalden  Building  very  high 
deformations  were  observed  in  the  concrete  of  the  beams  near  the 
supports;  so  high  that  the  results  were  doubted,  and  as  the  points 
on  the  load  deformation  curves  were  few  and  scattering,  there 
was  often  room  for  doubt.  For  this  reason  it  was  considered 
especially  important  that  evidence  which  would  confirm  or  dis- 
prove this  high  compression  in  the  concrete  be  obtained  in  the 

V    .oooa 
g  ^.oood 

^.0003 

^.oooz 

.0001 


.  D /stances  from  Capital  in  Inches. 

PIG.    5. — DATA    OF    FIG.    3    PLOTTED    AS    A    DISTANCE-DEFORMATION   DIAGRAM, 

POWERS  BUILDING. 

test  of  the  Turner-Carter  Building;  accordingly  the  method  of 
placing  observation  points  at  frequent  and  regular  intervals  along 
the  ends  of  the  beams  was  used.  The  deformations  measured 
are  plotted  in  Fig.  6  against  the  distance  from  the  supporting 
column,  and  the  results  not  only  tend  to  show  the  correctness  of 
these  measurements  but  also  to  indicate  that  the  high  stresses 
observed  in  the  beams  of  the  Wenalden  Building  were  actually 
present. 

Subjects  of  Investigation, — In  the  tests  discussed  in  this  paper 
deformations  have  been  measured  with  a  view  to  obtaining 
information  on  each  of  the  following  subjects: 


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180    Slater  on  Testing  Reinforced  Concrete  Buildings. 

(a)  The  values  of  the  moment  coefficients  at  the  center  and 
support  of  the  beam  or  slab  under  mvestigation. 

(6)  Relative  moments  at  support  for  various  conditions  of 
fixity. 

(c)  The  extent  to  which  the  floor  slab  acts  as  a  compression 
flange  of  the  floor  beam  to  produce  T-beam  action. 

(d)  Bond  stresses. 
{e)  Diagonal  tension. 
(/)  Stresses  in  columns. 

(gf)  Time  effect  under  constant  load. 


FIG.  6. — DISTRIBUTION  OF  COMPRESSIVE  DEFORMATION  IN  BOTTOM  OF  COLUMN 
BEAM,    TURNER-CARTER   BUILDING. 

(A)  The  lateral  distribution  of  stress  to  parts  of  the  structure 
entirely  outside  of  the  loaded  area. 

(i)  The  extent  to  which  reinforcement  stresses  are  modified 
by  errors  in  the  assumption  that  no  tension  is  carried  by  concrete. 

(j)  Stresses  in  slabs  of  beam  and  girder  construction. 

Other  subjects  of  investigation  have  received  attention,  but 
these  are  the  most  important  ones.  Some  phenomena  have  been 
observed,  offering  additional  problems,  of  which  the  determina- 
tion of  the  amount  of  arch  action  present  is  probably  the  most 
important.      It  is  important  both  in  itself  and  because  it  is 


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Slater  on  Testing  Reinforced  Concrete  Buildings.     181 

intimately  involved  in  the  determination  of  moment  coefficients. 
A  further  discussion  of  this  problem  is  here  given. 

The  attempts  to  determine  moment  coefficients  have  not 
been  entirely  successful  due  to  errors  of  measurement  and  unex- 
pected variations  in  similar  parts  of  the  structure  remote  from  each 
other.  The  method  has  been  to  measure  deformations  on  both 
reinforcement  and  concrete  at  the  center  and  support,  and  from 
these  measurements  to  determine  the  total  resisting  moment 
developed.  Equating  this  resisting  moment  to  a  constant  K 
times  Wl  a  solution  is  made  for  the  value  of  K,  The  indications 
that  arch  action  has  been  present  have  so  complicated  this  that 
even  where  measurements  have  appeared  quite  satisfactory,  the 
uncertain  amoimt  of  arch  action  entering  has  rendered  the  value 
of  K  uncertain. 

A  proposed  method  of  determining  the  amount  of  arch  action 
in  any  case  is  to  make  a  special  study  of  the  deformations  in  a 
cross-section  at  the  center  of  each  beam  across  an  entire  panel. 
In  this  study,  deformations  should  be  observed  on  the  reinforce- 
ment and  at  various  elevations  on  the  concrete  so  that  the  position 
of  the  neutral  axis  and  of  the  center  of  gravity  of  tensile  and  com- 
pressive stresses  respectively  can  be  accurately  located  without 
dependence  upon  the  law  of  conservation  of  plane  sections.  By 
this  means  it  should  'be  possible  to  determine  if  the  sum  of  the 
compressive  stresses  is  in  excess  of  that  of  the  tensile  stresses. 
If  so,  the  difiference  apparently  must  be  the  direct  thrust  due  to 
arch  action.  The  same  study  can  be  made,  though  not  so  satis- 
factorily, at  the  ends  of  the  beams.  This  measurement  of  thrust 
will  require  observations  on  an  extremely  large  number  of  gauge 
lines,  and  it  would  appear  important  to  concentrate  the  greater 
part  of  the  attention  of  the  test  on  one  panel. 

If  the  floor  be  considered  to  be  made  up  of  strip-beams  of 
differential  width  capable  of  transmitting  shear  from  strip  to  strip, 
it  is  not  necessary,  for  perfect  beam  action,  that  the  sum  of  the 
tensile  and  compressive  stresses  on  a  cross-section  of  any  one  strip 
be  zero.  However,  beam  action  does  require  that  the  sum  of  the 
tensile  and  compressive  stresses  on  the  total  cross-section  of  the 
beam  should  be  zero,  and  for  this  reason  it  is  important  to  extend 
the  investigation  sufficiently  to  determine  if  appreciable  deforma- 
tions are  continued  out  into  the  panel  adjacent  to  the  loaded  area. 


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182    Slater  on  Testing  Reinforced  Concrete  Buildings. 

Laborers, — The  number  of  laborers  which  can  be  used  advan- 
tageously will  depend  on  the  distance  from  which  the  loading 
material  is  to  be  transferred,  on  the  size  and  accessibility  of  the 
tested  area,  on  the  amount  of  work  which  can  be  done  by  them 
during  the  intervals  between  increments  of  loading  while  observa- 
tions are  being  taken,  and  on  the  length  of  time  required  to  take 
a  series  of  observations.  The  handling  of  the  labor  should,  if 
possible,  not  be  left  to  the  one  in  charge  of  the  test,  as  proper 


FIG.   7. — BRICK   AND   CEMENT   AS   A   LOAD,    WENALDEN   BUILDING. 

attention  to  the  conduct  of  the  test  demands  all  of  his  time.  In 
the  tests  included  in  this  paper  the  number  of  laborers  has  varied 
between  wide  limits,  from  5  or  6  in  the  Powers  test  to  30  or  35 
in  the  Deere  and  Webber  test. 

Loading. — ^In  the  tests  which  have  already  been  made,  the 
following  loading  materials  have  been  used:  brick,  cement  in 
bags,  loose  sand  in  small  boxes,  sand  in  sacks  and  pig  iron.  The 
material  used  will  almost  always  be  that  which  is  most  easily 
available,   because  the  moving  of  loading  material  from  any 


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Slater  on  Testino  Reinforced  Concrete  Buildinqs.    183 

distance  adds  very  greatly  to  the  cost  of  the  test.  Leaving  con- 
sideration of  cost  out  of  the  question,  sand  in  sacks  seems  to  be  the 
most  satisfactory  of  the  materials  above  mentioned  for  loading 
purposes.  Some  of  the  qualities  of  the  materials  mentioned  are 
as  follows: 

(a)  Brick:  Brick  spalls  and  chips  in  handling,  covering  the 
floor  with  dust  and  jagged  particles  which  cause  discomfort  to  the 
observer  in  kneeling  to  take  observations.     It  is  important  to 


PIG.  8. — SAND  IN  BOXES  AS  A  LOAD,   TUBNER-CABTER  BUILDING. 

avoid  this  because  discomfort  necessarily  decreases  the  accuracy 
of  his  observations.  This  might  be  avoided  by  sweeping,  but  in 
sweeping  it  is  diflScult  to  avoid  getting  dirt  into  holes  where  obser- 
vations are  to  be  taken,  and  this  is  just  as  troublesome  as  having 
the  dirt  on  the  floor.  Fig.  7  shows  the  use  of  both  brick  and  cement 
in  the  same  test.  Attention  is  called  to  the  proximity  of  the  cement 
sacks  to  the  beams  and  girders  of  the  floor  above.  In  some  cases 
the  intensity  of  the  load  would  be  limited  by  the  height  of  the 
ceiling  if  cement  and  brick  are  used. 


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184    Slateb  on  Testing  Reinforced  Concrete  Buildings. 

(6)  Cement:  Cement  sifts  through  the  sacks  and  the  sacks 
become  imtied,  scattering  cement  on  the  floor,  filling  observation 
holes  and  causing  much  dust  in  sweeping  or  cleaning  up.  The 
dust  is  injurious  to  delicate  instruments  and  annoying  to  observers 
and  recorders. 

(c)  Loose  Sand  in  Small  Boxes:  As  sand  is  usually  damp,  it 
does  not  have  the  fault  of  causing  dust  and  consequently  is  more 
easily  cleaned  up  than  the  other  materials  mentioned.  There  are, 
however,  other  objections  to  it.  In  filling  boxes  it  is  difficult  to 
avoid  spilling  the  sand  around  and  between  the  boxes,  and  con- 


FIG.  9. — BAND  IN  SACKS  AS  A  LOAD,  BARR  BUILDINQ  TEST^PANEL. 

sequently  filling  the  observation  holes.  On  account  of  the  great 
difficulty  in  removing  loose  sand  without  spilling  a  great  deal  of 
it,  it  is  impracticable  to  take  observations  as  the  load  is  being 
removed,  therefore  it  is  necessary  to  remove  in  one  increment  the 
whole  load  from  a  given  panel.  Fig.  8  shows  this  method  of  loading, 
(d)  Sand  in  Sacks:  Sand  in  sacks  constitutes  a  very  satis- 
factory loading  material.  Fig.  9.  It  was  piled  up  to  a  height  of 
about  9  or  10  ft.  and  very  little  inconvenience  was  caused  by  the 
sacks  becoming  untied  or  by  spillmg  the  sand.  The  worst  difficulty 
encountered,  and  this  exists  with  all  materials  handled  in  sacks, 
is  that  of  the  slidmg  of  sacks  on  themselves  when  the  load  is  piled 


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Slater  on  Testing  Reinforced  Concrete  Buildings.     185 

high.  It  can  be  seen  in  Fig.  9,  above  referred  to,  that  bracing 
was  necessary  to  prevent  the  sand  from  sHding  together  and 
filling  up  the  aisles.  It  is  a  source  of  danger  to  those  taking 
observations  as,  if  a  slide  should  occur,  it  would  probably  give 
very  little  warning  and  might  catch  the  observer  while  in  such  a 
position  that  he  could  not  escape.  However,  this  objection 
would  be  likely  to  occur  with  any  material  which  is  piled  as  high 
as  was  that  in  this  test.  Under  any  circumstances  it  is  necessary 
that  care  be  taken  and  undue  risks  avoided. 

(c)  Pig  Iron:   Pig  iron  was  used  as  loading  material  in  the 
test  of  the  Franks  Building,  Fig.  10.     From  the  standpoint  of 


i  FIG.    10. — pig  iron  as  a  LOAD     FRANKS  BUILDING, 

the  making  of  the  test,  the  worst  objection  to  it  is  that,  as  with 
the  brick,  small  particles  break  off  and  cause  annoyance  to  observ- 
ers. This  is  less  noticeable  than  with  brick  and  in  other  ways 
pig  iron  is  clean.  It  possesses  the  great  advantage  that  with  its 
use  a  very  heavy  load  can  be  applied  without  piling  the  load 
extremely  high. 

Tin  plate  in  boxes  2  ft.  square,  each  weighing  200  lb.,  was  to 
have  been  used  in  a  building  test.  A  more  nearly  ideal  loading 
material  would  probably  be  hard  to  find,  but  unfortunately  this 
test  could  not  be  carried  out. 

The  intensity  of  the  loading  will  depend  mainly  on  the  load 


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186    Slater  on  Testing  Reinforced  Concrete  Buildings.  , 

for  which  the  building  was  designed.  It  will  not  be  possible  to 
make  the  load  absolutely  uniform,  as  aisles  will  be  necessary  for 
the  purposes  of  (a)  convenience  in  placing  the  load,  (6)  access  to 
gauge  lines  for  the  taking  of  observations  and  (c)  prevention  of 


I 


mmk 


li 


FIG.  11. — MOMENT  AND  SHEAR  DIAGRAMS  FOR 
THREE  ARRANGEMENTS  OF  LOAD. 

arching  in  the  loading  materials.  It  has  been  found  that  it  is 
difficult  to  cover  more  than  about  75  per  cent  of  the  actual  area 
of  the  floor,  and  in  many  cases  less  than  this  will  actually  be 
covered.  Hence  in  computing  the  probable  height  of  the  load, 
this  fact  must  be  taken  into  consideration. 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    187 

Aisles  should  be  so  placed  that  the  load,  even  though  partly 
carried  by  archmg  of  the  material,  will  cause  stresses  in  the  floor 
which  are  approximately  equal  to  and  always  as  severe  as  those 
caused  by  an  actual  uniform  load.  Fig.  11  shows  the  moment 
and  shear  diagrams  which  would  be  obtained  by  loading  a  simple 
beam  with  a  total  load  W  distributed  over  the  span  in  three  dif- 
ferent ways,  as  follows: 

(a)  Solid  Line:  Uniform  load  W,  over  full  span. 

(6)  Broken  Line:  Same  load  W  distributed  over  one-half 
of  span,  giving  aisles  of  equal  width  at  center  and  support. 

(c)  Heavy  Dotted  Line:  Same  load  W  distributed  over 
one-half  span,  half  of  load  being  carried  by  arch  action  to  ends 
of  boxes  (shown  here  as  concentrated  loads  W/8),  and  the  other 
half  being  uniformly  distributed  over  the  half  span. 

It  will  be  possible  in  almost  any  test  to  arrange  the  loading 
material  in  such  a  way  as  to  come  within  the  limits  outlined  by  the 
three  arrangements  of  load  assumed  in  Fig.  11,  and  it  is  seen  that 
if  this  is  done,  the  presence  of  the  aisles  or  of  arching  to  the  sides 
of  the  boxes  or  piers,  while  not  affecting  the  amoimt  of  the  maxi- 
mmn  moment  and  the  maximum  shear,  would  tend  to  cause  them 
to  exist  over  greater  portions  of  the  span  than  would  be  the  case 
with  an  equal  imiform  load.  In  this  figure  aisles  equal  to  one- 
quarter  of  the  span  have  been  assumed.  In  no  case  would  they 
be  as  large  as  this,  and,  therefore,  the  moment  and  shear  diagrams 
should  actually  conform  even  more  nearly  to  those  for  uniform 
load  than  is  shown  in  the  figure. 

Arrangement  should  be  made,  if  possible,  to  store  the  loading 
material  near  the  test  area  to  hasten  the  work  of  applying  the 
load  after  the  test  begins.  The  general  rule  has  been  to  allow 
loadmg  material  to  be  stored  as  close  as  one  full  panel  length  from 
the  test  area,  but  the  intensity  of  the  storage  load  has  been  kept 
down  as  much  as  possible. 

preparation  for  the  test. 

Cutting  Holes  in  Concrete. — ^In  all  of  these  tests  it  is  necessary 
to  cut  holes  in  the  concrete  in  order  to  expose  the  reinforcement. 
Fig.  4  shows  a  hole  cut  in  the  concrete  of  the  Powers  Building 
where  a  series  of  measurements  was  taken  on  a  rod  passing  through 
a  column.     This  cutting  has  been  best  accomplished  by  the  use 


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188    Slater  on  Testing  Reinforced  Concrete  Buildings. 

of  a  cold  chisel  with  a  very  gradually  tapering  point.  This  is  a  task 
for  common  laborers  and  a  long  one  for  inexperienced  men,  but  it 
has  been  found  that  a  great  deal  of  speed  can  be  developed  by 
practice,  hence  the  importance  of  completing  this  part  of  the  work 
with  a  single  set  of  workmen. 

A  saving  in  mutilation  of  floors  can  often  be  effected  by 
planning  the  test  ahead  of  time  and  inserting  plugs  in  the  concrete 
during  construction  in  the  proper  position  for  the  gauge  lines. 
Removal  of  the  plugs  after  the  concrete  has  set  exposes  the  rein- 
forcement without  the  use  of  a  cold  chisel.  Likewise  metal  plugs 
may  be  set  in  the  concrete  at  the  proper  positions  for  the  measure- 
ment of  concrete  stresses  and  thus  save  cutting  into  the  concrete 
to  place  compression  plugs.  The  point  has  been  raised  that  by 
preparation  of  this  kind  a  chance  is  given  to  the  contractor  to 
know  what  panels  are  to  be  tested  and  thus  to  make  the  construc- 
tion of  that  panel  better  than  others.  For  this  reason  there  is 
room  for  question  as  to  the  advisability  of  using  this  method.  In 
most  of  the  tests  under  consideration  this  point  has  been  taken 
care  of  by  the  fact  that  it  was  not  known  until  shortly  before  the 
test  what  area  was  to  be  loaded.  It  is  believed  that  the  saving 
thus  effected  is  not  generally  sufficient  to  justify  prejudicing  the 
test  by  the  use  of  this  method. 

Drilling  of  the  gauge  holes  will  be  discussed  under  the  subject 
''Instruments  and  Observations. '' 

Scaffolding, — A  platform  supported  on  some  kind  of  scaffold 
is  necessary  which  will  enable  the  observer  to  get  close  enough  to 
the  floor  above  to  take  observations  of  deflection  and  deformation. 
This  should  be  at  such  a  height  that  when  the  observer  stands 
upon  it  the  points  where  measurements  of  deformation  are  to  be 
taken  will  be  about  one  inch  above  his  head.  For  flat  slab  con- 
struction this  condition  is  easily  obtained  (see  Fig.  12),  but  with 
beam  and  girder  construction  where  there  are  measurements 
on  beams,  girders,  and  the  floor  slab,  the  heights  df  different  gauge 
lines  are  so  different  that  arrangement  will  need  to  be  made  for 
building  certain  parts  of  the  platform  higher  than  others  (see  Fig. 
13).  It  is  important  that  the  elevation  of  the  platform  should 
be  such  that  the  observer  can  stand  erect  while  taking  the  readings, 
and  yet  such  that  the  instrument  will  not  be  too  high  for  convenient 
and  accurate  observation. 


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Slater  on  Testing  Reinforced  Concrete  Buildings.     189 

Another  framework  for  the  purpose  of  supporting  deflection 
apparatus  under  the  points  where  measurements  of  deflection 
are  to  be  taken  is  also  necessary.  In  order  that  the  movements 
of  the  observers  upon  the  observation  platform  may  not  jar  the 
deflection  apparatus,  the  two  frameworks  must  be  built  indepen- 
dently of  each  other.  In  all  the  tests  which  have  been  made,  up 
to  the  present  date,  these  deflection  frames  have  stood  on  the  floor 
and  have  been  braced  from  one  to  the  other  in  order  to  make  a 
comparatively  rigid  framework.  Fig.  12  shows  scaffolding  and 
deflection  frames  for  the  Franks  test.  An  objection  to  this  method 
of  measuring  deflections  is  that  changes  of  humidity  are  likely 


FIG.    12. — SCAFFOLDING   AND  DEFLECTION  FRAMES,   FRANKS  BUILDING. 

to  change  the  length  of  the  wooden  posts  used,  and  it  is  quite 
probable  that  an  improvement  could  be  made  in  the  form  of  this 
frame.  An  arrangement  which  has  been  suggested  consists  of 
steel  I-beams  supported  directly  by  the  columns  and  carrying 
other  steel  framework  on  which  can  be  placed  the  deflection 
apparatus.  This  would  give  more  nearly  a  self-contained  con- 
struction, and  the  changes  of  humidity  and  temperature  would 
not  change  the  deflection  readings,  except  as  the  length  of  column 
between  the  platform  thus  built  up  and  the  floor  above  is  changed. 
Equipment. — The  equipment  will  necessarily  consist  of  the 
following:   cutting  and  drilling  tools,  portable  lights  for  throwing 


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190    Slater  on  Testing  Reinforced  Concrete  Buildings. 

light  into  observation  holes,  note  books  and  facilities  for  doing 
drafting  and  for  reducing  data. 

The  cutting  and  drilling  tools  are  sufficiently  described  in 
other  paragraphs. 

Some  kind  of  a  portable  light  is  a  necessity,  as  gauge  lines  are 
often  located  in  dark  comers  and  as  observations  may  be  taken  at 
any  hour  of  the  day  or  night.     The  light  shown  in  Fig.  20  is  a 


PIG.    13. — PHOTOGRAPH    SHOWING    VARIATION    IN    HEIGHT    OP    GAUGE    UNES, 
TURNER-CARTER  BUILDING. 

hunter's  acetylene  light  and  is  quite  satisfactory.  The  light  is 
attached  to  the  forehead  and  may  be  thrown  in  various  directions 
according  to  the  setting  of  the  clamp  attachment.  The  acetylene 
tank  may  be  attached  to  the  belt  or  carried  in  the  pocket. 

Loose  leaf  note  books  should  be  provided  in  which  the  sheets 
are  as  large  as  can  be  conveniently  handled  and  filed.  The  forms  for 
record  shown  in  Fig.  29  are  very  conveniently  ruled  in  hectograph 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    191 

ink  and  copied  by  means  of  a  hectograph.  Printed  forms  might  be 
used,  but  so  many  differences  in  detail  are  made  to  correspond 
with  the  particular  test  in  question  that  this  would  not  be  advisable 
as  too  few  sheets  of  a  single  form  would  be  required  to  justify  the 
expense  of  having  them  printed. 

For  the  most  efficient  work  in  computing  results  and  making 
sketches  for  records,  it  is  important  that  an  adequate  place  be 
provided  where  some  privacy  may  be  had,  where  benches  and 
drafting  tables  may  be  used  and  where  instruments  and  other 
equipment  may  be  kept.  Fig.  14  shows  the  temporary  office 
which  was  provided  in  the  Turner-Carter  Building  test.     This 


PIG.    14. — TEMPORARY  OFFICE,   TURNER-CARTER  BUILDING. 

is  one  of  the  portable  office  shanties  which  the  Company  moves 
to  places  where  work  is  being  done.  The  photograph  shows  the 
interior  of  the  office  with  the  observers  and  recorders  at  work 
reducing  the  data  of  the  test.  This  added  equipment  will  add 
only  slightly  to  the  cost  of  the  test  and  very  greatly  to  the  efficiency 
of  the  work.  Special  attention  is  called  to  it  because  there  is  a 
tendency  to  neglect  this  part  and  to  think  of  it  as  only  a  secondary 
matter,  whereas  it  should  be  considered  as  one  of  the  most  impor- 
tant pieces  of  equipment. 

Summary  of  Test  Data. — ^A  summary  of  the  main  features 
of  the  building  tests  discussed  in  this  paper  is  presented  in  Table  I, 
as  it  is  believed  that  the  information  given  there  will  be  of  assist- 


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192     Slater  on  Tbbtino  Reinforced  Concrete 

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Slater  on  Testing  Reinforced  Concrete  Buildings.     193 

ance  in  the  efficient  planning  of  and  preparation  for  such  a  test. 
The  foUowing  notes  are  in  explanation  of  data  given  in  this  table: 

The  figures  giving  area  of  test  show  the  total  area  of  the  floor 
covered  and  do  not  count  any  area  twice  even  though  loaded 
twice  as  was  done  in  the  WenaJden  Building  test.  It  does  include 
the  area  of  separate  singly  panel  tests  which  were  made  in  the 
Wenalden  and  Franks  tests. 

The  maximum  test  load  in  lb.  per  sq.  ft.  is  given  in  the  column 
under  that  caption.  In  some  cases  this  was  over  only  a  part  of 
the  test  area.  The  proportional  parts  of  the  test  area  having  the 
maximum  load  applied  were  as  foUows:  Wenalden  80  per  cent, 
Powers  50  per  cent,  Franks  40  per  cent,  all  others  100  per  cent. 

The  column  giving  the  amount  of  load  handled  includes  the 
rehandling  due  to  change  of  position  of  loads.  The  proportionate 
parts  of  the  loads  rehandled  in  this  way  were  Wenalden  40  per  cent. 
Powers  60  per  cent,  Franks  80  per  cent.  In  all  the  other  tests  no 
load  was  rehandled. 

The  column  giving  the  number  of  observers  includes  only 
those  reading  deformations.  In  the  Wenalden  and  Powers  tests 
another  observer  took  deflection  readings.  In  the  Powers  test 
and  the  Barr  tests,  almost  all  the  deformation  readings  were  taken 
by  each  of  two  observers,  giving  a  larger  number  of  gauge  lines 
per  observer  than  in  the  other  tests. 

III.    Instruments  and  Observations. 

Exiensometers. — ^In  the  past  the  great  obstacle  to  the  measure- 
ment of  deformations  in  building  tests  has  been  the  difficulty  of 
attaching  the  measuring  instruments  to  either  the  reinforcement 
or  the  concrete  on  the  flat  surface  of  a  floor,  and  recent  tests  show 
the  necessity  of  making  measurements  of  reinforcement  deforma- 
tion directly  on  the  reinforcement.  A  satisfactory  method  of 
accomplishing  this  has  been  provided  by  the  introduction  of  the 
extensometer  invented  by  H.  C.  Berry  of  the  University  of  Penn- 
sylvania and  adapted  to  this  work  by  improvements  made  at  the 
University  of  Illinois.  This  instrument  is  similar  in  some  respects 
to  the  strain  gauge  designed  and  used  as  long  ago  as  1888  by 
James  E.  Howard,  then  Engineer  of  Tests  at  Watertown  Arsenal, 

The  great  value  of  this  instrument  in  building  tests  lies  in  the 
following  facts:  (a)  Its  use  makes  it  possible  to  take  measurements 


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194    Slater  on  Testing  Reinforced  Concrete  Buildinos. 


directly  upon  the  surface  of  the  reinforcement  and  concrete. 
(6)  With  its  use  there  is  no  apparatus  left  in  place  to  be  damaged 
or  disturbed  during  loading,  (c)  Due  to  the  fact  that  it  is  portable, 
measurements  may  be  taken  in  a  large  number  of  places  with  a 
single  instrument.       Measurements  have  been  taken  at  as  many 


-S^et^  Lirrm. 


Ecc&ntnc  hole  Central  hole 

Finishinq 
tool, 

FIG.    15. — UNIVERSITY   OF  ILLINOIS   EXTENSOMETER. 


as  104  points  in  a  single  test.  This  would  call  for  an  outlay  of 
from  11200  to  $2500  for  instruments  if  fixed  instruments  were  used. 
Fig.  15  shows  the  Illinois  extensometer  in  its  present  form. 
Any  movement  of  the  point  B  due  to  a  change  in  the  length  of  the 
gauge  line  is  transmitted  to  the  Ames  gauge  through  vertical 
movement  of  point  C,  by  means  of  the  leg  BD  and  the  arm  DC 
pivoted  at  D.  The  Ames  gauge  is  sensitive  to  a  movement  at  C 
of  .0001  in.     The  ratio  of  the  length  CD  to  the  length  BD  is 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    195 

approximately  5  and  the  Ames  gauge  is  thus  sensitive  to  a  move- 
ment at  B  of  .00002  in.  (.0001  rD.-r-S).  However,  this  must  not 
be  taken  to  mean  that  the  extensometer  possesses  this  degree  of 
accuracy  in  measuring  stresses,  since  some  movement  of  the  point 
of  the  leg  at  B  is  certain  to  result  from  variation  in  the  handling 
of  the  instrument. 

To  obtain  the  exact  ratio  between  movements  at  points  B 
and  C  the  instrument  is  calibrated  by  means  of  a  Brown  and  Sharpe 
screw  micrometer.  For  known  movements  of  the  point  B  readings 
of  the  Ames  gauge  are  taken  and  a  calibration  curve  plotted  for  the 
entire  range  of  the  instrument. 

The  first  instrument  of  this  type  built  by  the  Engineering 


FIG.    16. — BERRY   EXTENSOMETER. 

Experiment  Station  of  the  University  of  Illinois  was  made  by 
arrangement  with  Mr.  Berry  for  the  Deere  and  Webber  test. 
It  was  designed  by  H.  F.  Moore  and  A.  E.  Lord,  and  was  like  the 
instrument  in  use  at  present  except  that  it  had  a  15-in.  gauge 
length  and  was  made  entirely  of  steel.  Later  on  in  making  the 
instrument  for  general  use  aluminum  was  substituted  for  steel  in 
order  to  reduce  its  weight  and  the  gauge  length  was  made  variable 
from  6  to  11  in.  Since  then  several  minor  changes  have  been 
made.  The  legs  have  been  made  stiflfer  in  order  to  reduce  the 
error  due  to  unconsciously  applied  longitudinal  thrust  and  the 
points  have  been  made  sharper  in  order  to  reduce  the  pressure 
required  in  seating  the  instrument.  These  improvements  have 
reduced  the  probable  error  of  observation  considerably. 


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196    Slater  on  Testing  Reinforced  Concrete  Buildings. 

The  extensometer  loaned  by  Mr.  Berry  to  the  University  of 
Illinois  in  1910  and  used  in  the  Deere  and  Webber  test  is  shown  m 
Kg.  16.  It  differs  from  the  Illinois  instrument  in  that  the  move- 
ment of  the  multiplying  arm  is  measured  by  means  of  a  screw 
micrometer  instead  of  the  Ames  gauge  head,  the  point  of  contact 
of  the  micrometer  plimger  and  the  lever  arm  being  determined 
by  means  of  a  telephone  apparatus.  The  screw  micrometer  and 
the  frame  of  the  extensometer  are  insulated  from  each  other  and 
are  connected  with  the  poles  of  a  small  battery  by  means  of  copper 
wires.  A  contact  between  the  plimger  of  the  screw  micrometer  and 
the  multiplying  lever  completes  the  circuit  and  the  current  set  up 
produces  a  vibration  of  the  diaphragm  of  the  telephone  apparatus 


PIG.   17. — LATEST  TYPE  OF  BERRT  EXTENSOMETER. 

carried  on  the  head.  This  method  of  observation  is  very  slow  and 
the  apparatus  gets  out  of  order  very  easily, 

The  use  of  the  Ames  gauge  head  instead  of  the  screw 
micrometer  and  telephone  apparatus  adopted  by  Mr.  Moore  in 
the  instrument  used  in  the  Deere  and  Webber  test  has  greatly 
facilitated  the  use  of  the  extensometer.  The  legs  of  this  instru- 
ment also  were  made  longer  in  order  to  adapt  it  to  the  measure- 
ment of  deformations  of  reinforcement  imbedded  in  concrete. 
Both  of  these  modifications  have  later  been  used  by  Mr.  Berry  in 
instruments  which  he  has  put  on  the  market. 

The  extensometer  more  recently  designed  by  Mr.  Berry  is 
shown  in  Fig.  17.     It  is  not  different  in  principle  from  the  one 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    197 

just  described.  It  differs  from  the  IlUnois  instrument  in  the 
following  details:  (a)  Instead  of  having  a  uniformly  variable 
gauge  length  ranging  from  6  to  11  in.  it  has  two  fixed  gauge 
lengths  of  2  in.  and  8  in.  respectively.  (6)  The  instrument  shown 
here  has  a  multiplication  ratio  of  two  between  leg  and  arm,  and 
in  order  to  make  this  ratio  five  (as  in  the  Illinois  type)  it  is  nec- 
essary to  use  a  leg  which  is  only  one  inch  long.  With  this 
arrangement  the  instrument  can  not  usually  be  used  for  meas- 
uring deformations  in  reinforcing  bars,  owing  to  their  depth  of 
imbedment.  (c)  This  instrument  is  put  out  with  framework  of 
Invar  steel  or  aluminum.     While  Invar  steel  makes  the  weight 


FIG.    18. — BERRY  EXTENSOMETER  AS  MODIFIED  BY  TRELEASE. 

somewhat  greater  than  that  of  the  aluminum  instruments,  it  has 
the  great  advantage  that  so  great  dependence  on  an  Invar  steel 
standard  bar  is  avoided  and  the  study  of  the  temperature  changes 
in  the  reinforcement  and  concrete  of  the  structure  is  accomplished 
with  greater  ease. 

F.  J.  Trelease  of  the  Corrugated  Bar  Company  has  designed 
an  instrument  of  the  Berry  type  and  has  used  it  in  at  least  one 
test.  This  instrument,  shown  in  Fig.  18,  also  has  as  its  main 
feature  a  multiplying  lever  which  actuates  the  plunger  of  an  Ames 
gauge  head.  The  principal  difference  between  this  instrument 
and  the  one  shown  in  Fig.  15  is  that  the  multiplying  lever  is 


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198    Slater  on  Testing  Reinforced  Concrete  Buildings. 

vertical  instead  of  horizontal.  Results  have  been  obtained  with 
it  which  do  not  differ  much  as  to  accuracy  with  those  of  the 
Illinois  type  of  instrument. 

Use  of  Berry  Extensometer. — In  obtaining  good  results  with 
this  extensometer,  a  great  deal  depends  upon  careful  manipula- 
tion of  it.  Two  things  which  are  of  great  importance  in  this 
respect  are  (a)  the  preparation  of  the  gauge  holes,  and  (b)  care 
and  experience  in  the  use  of  the  instrument. 

The  exact  gauge  length  is  best  secured  by  the  use  of  some 


FIG.    19. — INSTRUMENTS   AND   TOOLS. 

kind  of  gauge  marker  such,  for  instance,  as  is  shown  in  Fig.  19 
used  for  marking  points  where  gauge  holes  are  to  be  drilled.  In 
the  work  of  the  Illinois  Engineering  Experiment  Station  the  holes 
are  drilled  with  a  No.  54  drill  (.055  in.  in  diameter).  At  the 
beginning  of  the  use  of  the  Berry  extensometer  a  number  E 
countersink  drill  (approximately  3/32  in.  in  diameter)  was  used, 
but  a  smaller  one  seems  to  be  better,  because  it  is  easier  to  get  the 
properly  finished  hole,  and  because  a  slight  eccentricity  of  the 
gauge  holes  on  the  reinforcing  rod  causes  less  error  in  manipula- 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    199 

tion  of  the  extensometer  when  a  small  drill  is  used.  In  the  case 
of  measurements  on  small  rods  also,  the  3/32  in.  drill  cuts  away 
a  large  percentage  of  the  metal  in  the  rods.  Up  to  the  present 
time,  for  drilling  these  gauge  holes  a  breast  drill  has  been  used 
which  is  geared  so  that  one  revolution  of  the  crank  gives  about 
4^  revolutions  of  the  drill.  In  the  hands  of  a  skilled  workman 
very  satisfactory  work  can  be  done  in  this  way,  but  where,  as 
quite  frequently  will  be  the  case,  the  drilling  has  to  be  done  by 
persons  not  familiar  with  this  kind  of  work,  something  better  is 
needed.  A  drill  driven  by  a  flexible  cable  attached  to  a  small 
electric  motor  giving  a  speed  of  rotation  of  400  r.  p.  m.  and 
upwards  probably  would  be  much  better.  Where  high  carbon 
steel  has  been  encountered  many  drills  have  been  broken  and 
even  when  a  hole  was  drilled  a  poor  job  has  often  been  the 
result.  After  drilling  the  holes,  the  edges  should  be  finished  to 
remove  the  burr  and  to  round  off  the  sharp  comers.  The  tool 
shown  in  Fig.  15  is  designed  to  accomplish  this  purpose.  Such 
a  tool  should  not  be  a  cutting  tool  but  rather  a  wearing  or  polish- 
ing tool.  A  pointed  magnet  to  remove  steel  dust  and  small  frag- 
ments of  steel  torn  off  in  drilling  would  be  of  use.  It  is  hard  to 
place  too  much  emphasis  on  the  proper  preparation  of  gauge 
holes. 

Standard  Bar. — While  the  careful  preparation  of  gauge  holes 
is  important,  not  less  so  is  the  use  of  a  standard  bar.  The  neces- 
sity for  it  was  first  found  in  the  test  of  the  Deere  and  Webber 
Building.  Variation  in  temperature  was  sufficient  to  cause  a 
change  in  the  length  of  the  instrument  as  great  in  many  cases  as 
that  in  the  reinforcement  due  to  the  applied  load.  Hence  it  was 
found  necessary  to  make  observations  on  an  unstressed  standard 
bar  showing  any  temperature  changes  in  the  length  of  the  instru- 
ment. In  this  test  a  bar  of  about  |-in.  steel  was  used  as  a  stand- 
ard. It  was  protected  from  rapid  temperature  changes  by 
imbedment  in  plaster  of  Paris,  but  kept  on  the  floor  where  the 
test  was  being  made.  In  this  way  it  was  expected  to  make  the 
change  in  the  length  of  the  standard  bar  due  to  temperature 
variations  about  equal  to  the  change  in  length  of  the  reinforce- 
ment due  to  the  same  cause.  To  some  extent  this  purpose  was 
accomplished,  but  as  the  plaster  covering  was  thin  and  not  very 
dry  the  change  in  the  standard  bar  must  have  been  much  more 


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200    Slater  on  Testing  Reinforced  Concrete  Buildings. 

rapid  than  that  in  the  reinforcement.  In  the  test  of  the  Wenal- 
den  Building  precautions  were  taken  to  imbed  the  standard  bar 
in  concrete.  This  practice  has  been  kept  up  in  tests  made  since 
then,  and  in  addition  standard  gauge  lines  have  been  established 
in  parts  of  the  floor  not  affected  by  the  load.  These  latter  have 
been  placed  both  on  the  reinforcement  and  in  the  concrete.  Fig. 
20  shows  the  taking  of  an  observation  on  a  standard  gauge  line 
in  the  Turner-Carter  test.     It  can  be  seen  that  it  is  located  in  a 


Fia.  20. — TAKING  AN  OBSERVATION  ON  STANDARD  GAUGE  LINE,  TURNER-CARTER 

BUILDING. 

part  of  the  floor  entirely  away  from  the  loaded  area.  The  great- 
est development  in  the  use  of  the  standard  bar  has  been  in  the 
frequency  of  reference  to  it  and  in  the  development  of  an  exact 
system  for  the  calculation  of  temperature  corrections.  It  was 
previously  noted  that  a  steel  instrument  was  used  in  the  Deere 
and  Webber  test  but  that  in  the  subsequent  tests  an  aluminum 
instrument  was  used.  Since  the  coefficient  of  expansion  for 
aluminum  is  almost  twice  that  for  steel,  it  is  apparent  that 
dependence  on  the  standard  gauge  line  must  have  been  of  still 


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Slater  on  Testing  Reinforced  Concrete  Buildings.   201 

greater  importance  in  the  later  tests.  Difficulty  was  found  in 
interpreting  the  notes  taken  on  the  Wenalden  test,  but  the 
greater  dependence  on  the  standard  gauge  line  and  the  more 
systematic  use  of  it  observed  since  then  has  very  largely  overcome 
this  difficulty.  Subsequent  to  the  completion  of  the  last  building 
test  participated  in  by  the  writer,  standard  bars  of  Invar  steel 
have  been  secured.  Invar  steel  has  a  coefficient  of  expansion 
only  about  one-sixth  that  of  ordinary  steel  and  its  use  as  a  stand- 
ard bar  makes  it  possible  to  eliminate  from  the  results  almost  all 
the  eflfects  of  temperature  variation.  If  it  is  desired  to  determine 
how  great  are  the  temperature  eflfects,  a  standard  gauge  line  can 
be  placed  in  the  floor  as  before  in  such  a  position  as  not  to  be 
aflfected  by  the  floor  load. 

It  has  been  the  practice  in  the  more  recent  building  t^sts  for 
each  observer  to  make  observations  regularly  on  two  standard 
gauge  lines.  This  is  done  so  that  one  may  form  a  check  on 
the  other.  If  only  one  were  used,  a  large  accidental  change  in 
the  readings  due  for  instance  to  sand  in  the  gauge  holes  might  be 
mistaken  for  a  temperature  effect.  If  two  standards  are  used, 
any  such  accidental  change  as  the  above  would  seldom  be  the 
same  in  both,  and  the  error  would  be  detected.  An  accident  to 
the  instrument  would  probably  cause  the  same  change  on  both 
standard  gauge  lines  and  the  use  of  the  two  standards  would  not 
help  to  detect  this  kind  of  an  error.  However,  such  errors  are 
usually  so  large  as  to  be  apparent  in  any  standard  reading  and 
are  infrequent  as  compared  with  errors  due  to  filling  of  the  gauge 
holes. 

Deflection  Instruments. — In  the  building  tests  described  in 
this  paper  deflection  instruments  of  two  types  have  been  used, 
one  being  that  used  by  the  Illinois  Enghieering  Experiment 
Station  and  the  other  that  used  by  the  Corrugated  Bar  Company. 
The  former,  shown  in  Fig.  21,  consists  of  a  screw  micrometer  head 
of  1  in.  travel,  connected  in  tandem  with  an  Ames  gauge  head 
micrometer  of  |  in.  travel.  The  screw  micrometer  is  designed 
to  cover  large  variations  in  deflections,  and  the  Ames  gauge 
head,  small  ones.  Fig.  21  shows  also  the  method  of  using  this 
deflectometer.  A  plate,  having  a  ^-in.  steel  ball  attached,  is 
plastered  to  the  surface,  deflections  of  which  are  to  be  measured. 
A  |-in.  bolt,  which  has  a  steel  ball  inserted  into  its  upper  end, 


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202   Slater  on  Testing  Reinforced  Concrete  Buildings. 

is  set  into  a  wooden  block  (part  of  the  deflection  framework)  in 
such  a  way  that  its  elevation  can  be  adjusted  to  give  any  desired 
zero  reading  of  the  deflectometer.  Thus  at  the  beginning  of  a 
test  all  the  zero  deflection  readings  can  be  determined  so  that  for 
a  considerable  length  of  time  all  the  change  in  deflection  will  be 
shown  on  the  Ames  gauge  without  any  change  of  the  screw 
micrometer.     As  larger  changes  take  place,  a  second  setting  of 


Concr^fm   Floor 


kVooden         ■■ 


FIG.  21. — DEFLECTOMETER,  UNIVERSITY  OF  ILUNOIS. 

the  screw  micrometer  will  probably  be  necessary.  The  great 
advantage  of  this  instrument  is  the  rapidity  with  which  it  can  be 
used.  It  has  been  found  to  work  very  satisfactorily  in  most 
respects.  A  shortcoming,  however,  has  been  the  lack  of  a  revolu- 
tion counter  on  the  Ames  gauge  so  that  in  case  of  large  changes 
of  deflection  it  is  possible  to  make  an  error  of  as  much  as  0.1  in. 
in  interpreting  the  readings,  though  this  is  very  unlikely.  This 
instrument  was  last  used  in  the  Turner-Carter  test  and  since  then 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    203 

an  Ames  gauge  head,  which  has  a  revolution  counter,  has  been 
provided  for  it,  so  that  the  diflSculty  here  mentioned  is  not  likely 
to  occur  in  the  future. 

The  deflectometer  used  by  the  Corrugated  Bar  Company  is 
shown  in  Fig.  22  and  consists  of  a  screw  micrometer  depth  gauge 
by  means  of  which  distances  for  varying  loads  are  measured 
between  the  stationary  frame  and  a  point  on  the  beam  or  floor 

/     XT' '^  '  i//////P//////^//i//P/ ' ^'V^ii'f^FA c* -  V ^ ■ '/ 


tnakh  Micrometer'^ 


Fia.  22. — DEFLECTOMETER,   CORRUGATED  BAR  COMPANY. 

slab.  It  has  the  advantage  over  the  one  previously  described 
that  actual  distances  are  measured  instead  of  changes  in  dis- 
tance, so  that  if  the  complete  reading  is  taken  each  time,  there  is 
no  possible  way  of  misinterpreting  results.  It  has  also  the  advan- 
tage of  a  much  larger  range  of  measurement.  In  the  Barr  panel 
test  a  gross  deflection  of  more  than  3  in.  took  place.  As  the 
Illinois  type  of  deflectometer  has  a  range  of  only  \\  in.  it  could 
not  have  been  used  in  this  test.     This,  however,  is  more  than 


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204   Slater  on  Testing  Reinforced  Concrete  Buildings. 

would  often  if  ever  occur  in  the  test  of  a  building.  Its  disadvan- 
tage is  that  it  requires  a  longer  time  to  make  an  observation  than 
does  the  deflectometer  previously  described. 

Observers, — Observers  should  be  experienced  in  the  use  of  the 
Berry  extensometer  before  imdertaking  work  on  a  field  test.  The 
chances  of  error  in  the  manipulation  of  the  instrument  are  large 
and  as  a  rule  the  deformations  measured  are  small,  so  that  the 
error  is  likely  to  be  quite  a  large  proportion  of  the  total  measure- 
ment; hence  it  is  important  to  reduce  errors  to  the  lowest  pos- 
sible limit. 

Extensometer  Observations. — ^If  the  observations  at  zero  are 
equally  as  good  as  other  observations,  a  curve  may  be  drawn 
through  all  the  points  of  any  load-deformation  diagram  after  the 
test  is  completed,  weighting  the  zero  observations  equally  with 
the  others  and  the  zero  point  shown  by  the  most  probable  curve 
should  be  used  as  the  origin.  This  method  involves  waiting  until 
the  completion  of  the  test  to  draw  these  curves.  It  would  be 
better  to  spend  much  more  time  on  the  zero  observations,  in  order 
to  make  them  reliable,  than  is  paid  to  any  other  series.  By  this 
means  a  check  can  be  had  upon  the  action  of  the  structure  as  the 
test  progresses  and  the  construction  of  the  most  probable  curve 
will  be  made  more  simple.  To  do  this  it  is  essential  that  several 
complete  series  of  zero  observations  should  be  taken  with  no 
load  on  the  floor,  and  it  would  be  weU  to  repeat  this  through 
considerable  range  of  temperature  to  study  temperature  efifect 
on  the  reinforcement  and  on  the  concrete.  This  study  was 
attempted  in  the  Deere  and  Webber  test,  but  the  changes  both  in 
instruments  and  in  reinforcement  were  included  in  the  measure- 
ments and  could  not  be  separated,  so  no  definite  conclusions 
could  be  drawn.  However,  with  an  Invar  steel  standard  bar  or 
with  an  instrument  made  of  Invar  steel  these  two  kinds  of 
changes  can  be  separated  and  to  some  extent  at  least  the  effect 
of  temperature  determined. 

In  taking  an  ordinary  observation  about  five  readings  should 
be  averaged.  In  all  of  the  building  tests  which  have  been  made, 
individual  extensometer  readings  were  recorded,  but  in  laboratory 
tests  the  practice  of  averaging  the  results  mentally  has  been 
adopted.  This  gives  very  satisfactory  results  for  laboratory  tests 
and  saves  a  great  deal  of  time.     It  is  possible  that  this  practice 


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Slater  on  Testing  Reinforced  Concrete  BmLDiNGS.    205 

could  be  adopted  for  field  tests  also.  It  would  save  time  on  a 
test  and  with  a  good  recorder  the  calculations  could  be  kept  up 
with  the  observations.  In  the  more  recent  building  tests  the 
practice  followed  in  obtaining  readings  for  any  observation  has 
been  to  reject  all  readings  until  5  consecutive  ones  have  been 
obtained  which  agree  within  .0004  in.  These  five  consecutive 
readings  then  are  averaged  to  form  an  observation. 

Deflectometer  observations  have  been  suflSciently  discussed 
in  the  description  of  the  deflectometer  and  will  not  be  taken  up 
again  here. 

Observation  of  Cracks. — ^Up  to  very  recently  the  observation 
of  cracks  has  been  considered  one  of  the  most  important  features 
of  a  test,  and  if  carefully  done  it  may  yet  add  considerable  to  the 
confidence  in  the  results.  These  observations  should  be  made 
and  recorded  for  zero  load  and  at  each  increment  of  load.  This 
is  one  of  the  most  tedious  parts  of  the  test,  and  to  carry  it  out 
faithfully  requires  a  great  deal  of  patience.  The  examination 
should  be  minute  and  very  thorough.  One  who  is  not  familiar 
with  this  kind  of  work  will  be  likely  to  miss  important  indications 
and  careful  supervision  should  be  maintained  over  this  part  of 
the  investigation. 

Special  attention  has  been  called  to  observation  of  cracks 
because  of  incorrect  ideas  which  apparently  prevail  with  regard 
to  them.  It  seems  to  be  the  idea  of  some  engineers  that  the  type 
of  construction  advocated  by  themselves  is  immune  from  cracks. 
When  it  is  remembered  that  plain  concrete  fails  in  tension  at  a 
unit  deformation  of  about  .0001,  it  is  apparent  that  cracks  must 
form  when  the  stress  in  the  reinforcement  is  such  as  to  correspond 
with  this  deformation,  or  at  about  3000  lb.  per  sq.  in.  At  this 
stage  the  cracks  are  often  too  small  for  detection  with  the  naked 
eye,  but  almost  always  very  fine  cracks  are  foimd  at  stresses 
ranging  between  3000  and  10,000  lb.  per  sq.  in.  Thus  to  report 
for  a  floor  loaded  to  twice  the  designed  load  that  no  cracks  were 
observed  is  to  admit  one  of  three  things,  namely,  that  an  excess 
of  reinforcement  was  used,  suflScient  care  in  taking  observations 
was  lacking,  or  that  not  all  the  facts  of  the  case  were  reported. 

It  should  be  borne  in  mind  that  the  cracks  referred  to  in 
this  pAper  are  often  extremely  minute  and  usually  are  not  visible 
to  a  casual  observer.     Frequently  cracks  have  been  traced  with 


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206    Slater  on  Testing  Reinforced  Concrete  Buildings. 

a  lead  pencil  to  make  them  distinct  for  the  purpose  of  sketching, 
and  it  seems  apparent  that  some  persons  visiting  the  test  have 
mistaken  these  pencil  marks  for  large  cracks.  At  any  rate  reports 
have  been  circulated  as  to  the  existence  of  large  cracks  in  a  test 
where  to  the  writer's  personal  knowledge  there  were  none. 

ACCURACY  OF  DEFORMATION  MEASUREMENTS. 

Probable  Error. — The  ratio  of  multiplication  in  the  Berry 
extensometer  is  not  exactly  equal  to  the  ratio  of  the  length  of  the 
arm  to  the  length  of  the  leg,  the  error  being  due  to  the  fact  that 
the  plunger  of  the  Ames  gauge  head  does  not  always  travel  in  a 
line  perpendicular  to  the  multiplying  lever.  However,  calcula- 
tions show  that  this  approximation  results  in  an  error  in  the 
measurement  of  reinforcement  stresses  equal  to  only  about  one- 
quarter  of  one  per  cent  for  an  extreme  case.  It  may  be  seen  later 
that  errors  of  observation  are  large  enough  in  proportion  that  this 
error  can  be  neglected. 

In  forming  a  basis  for  a  conclusion  as  to  the  accuracy  of  the 
figures  given  out  as  results  of  tests,  use  has  been  made  of  the  check 
readings  taken  by  two  observers  on  the  same  gauge  lines  and  of 
calculated  probable  error  of  the  means  of  five  readings.  While 
it  is  possible  to  calculate  with  some  accuracy  the  probable  error 
of  replacing  the  instrument  on  the  same  gauge  line  time  after 
time  at  one  sitting,  it  is  very  difiScult  to  determine  the  error  caused 
by  gradually  cramping  the  quarters  of  the  observer  as  the  loading 
material  piles  up.  A  determination  of  errors  based  on  independent 
checking  by  a  second  observer  should  be  expected  to  eliminate 
to  a  large  extent  errors  of  all  kinds  and  the  greatest  dependence 
should  be  placed  on  this  kind  of  results. 

In  the  test  of  the  Powers  Building  most  of  the  observations 
taken  were  checked  by  a  second  observer  and  some  of  the  results 
are  shown  in  the  load  stress  curves  of  Fig.  23.  The  values  shown 
in  solid  circles  were  observed  by  F.  J.  Trelease  and  those  in  open 
circles,  by  the  writer.  The  zero  reading  for  the  latter  is  in  each 
case  at  a  load  of  50  lb.  per  sq.  ft.,  and  in  order  to  make  a  direct 
comparison  of  results,  all  these  curves  must  be  set  over  so  that 
their  zeros  coincide  with  the  stress  values  at  50  lb.  per  sq.  ft.  of 
Mr.  Trelease's  curves.  Having  made  this  correction  the  average 
variation  between  all  the  comparable  points  is  about  670  lb.  per 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    207 

sq.  in.  (.0000223  unit  deformation),  which  amounts  to  a  probable 
error  of  approximately  ±340  lb.  per  sq.  in.  (±.000011  unit 
deformation). 

Fig.  24  shows  the  results  of  a  series' of  measurements  taken  in 
the  same  way  on  the  upper  and  lower  surfaces  of  a  4  x  4  in.  timber 
beam  loaded  with  sacks  of  sand  on  a  12-ft.  span.  The  points  in 
open  circles  represent  measurements  on  the  top  surface  and  those 
in  crosses  on  the  bottom  surface.     Determined  in  the  same  way, 


S  S  S  S     ^ 

lo  lo  ^  "o     o 

Si'ee/  Sfress  mlh  per  S(f  /n. 

FIG.   23. — LOAD-STRESS  DIAGRAMS   OF  TWO   OBSERVERS,   POWERS  BUILDING. 

these  measurements  show  an  average  probable  error  of  approxi- 
mately =*=  .000017  unit  deformation.  As  previously  stated,  these 
check  measurements  must  be  taken  to  give  results  more  applicable 
than  calculations  of  probable  error  of  the  mean  of  a  group  of 
readings.  However,  it  may  be  expected  that  where  an  increase 
in  accuracy  of  setting  the  instrument  is  found,  a  decrease  in  error 
due  to  cramped  quarters,  etc.,  will  also  be  found.  In  Fig.  25  is 
given  a  curve  which  shows  for  each  of  four  building  tests  the 
probable  error  of  the  average  of  five  readings.    Each  plotted  point 


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208    Slater  on  Testing  Reinforced  Concrete  Buildings. 

is  the  average  of  the  probable  errors  calculated  for  six  different 
gauge  lines  at  a  given  load.  What  this  diagram  may  be  expected 
to  show  is  the  improvement  in  results  with  increased  experience 
rather  than  the  actual  value  of  the  probable  error.  The  marked 
improvement  in  results  shown  here  is  due  in  part  to  increased 
skill  in  the  observer  and  in  part  to  improvement  in  the  instrument 
itself.  Fig.  26  gives  a  curve  showing  deformations  in  a  bottom  bar 
of  the  Barr  test  panel  as  shown  in  the  sketch.     The  points  shown 


ZOO  AOO  600 

L  oad  in  Pounds 

FIG.  24. — LOAD-DEFORMATION  DIAGRAMS  OF  TW'O  OBSERVERS;    TEST  OP  A 
4  X  4-IN.   TIMBER   BEAM. 

as  open  circles  are  for  a  load  of  590  lb.  per  sq.  ft.  and  solid  circles 
are  for  a  load  of  615  lb.  per  sq.  ft.  This  is  the  best  curve  the 
writer  has  been  able  to  obtain  on  any  building  test  and  it  can  not 
be  taken  as  representative,  but  rather  to  illustrate  what  may  be 
obtained  under  the  best  conditions.  The  regularly  varying  differ- 
ences for  a  small  difference  of  loads  indicate  that  the  stresses 
must^have  been  determined  correctly  within  a  very  small  range. 
A  study  of  probable  error  was  made  in  the  Turner-Carter 
test  by  the  use  of  a  series  of  100  observations  taken  by  each  of  the 


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Slater  on  Testing  Reinpobced  Concbetb  Buildinos.    209 


^/OOO 


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eoo 


eoo 


^  400 


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of  Tests 


PIG.  25. — AVERAGE  PROBABLE  ERROR  FROM  FOUR  BUILDING  TESTS. 


JO0O5 
\.0003 

\jOOOB 
^.0003 


Load'd/L  '^  It  per  t  "cf  Ft- 


iK^  7^t3g0Z  \pffr  S(^/-  P" 


1§  %  I  ^  8" 

Distance  in  Inches  from  Edge  of  Beam 


FIG.  26. — DEFORMATION  ALONG  BOTTOM   REINFORCING  BAR,   BAR  PANEL  TEST. 


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210     Slater  on  Testing  Reinforced  Concrete  Buildings. 

two  observers  on  two  gauge  lines  selected  as  likely  to  give  the  most 
and  the  least  accurate  results.  The  results  of  this  study  are  given 
in  Table  II. 


TABLE  II — ^Probable  Error  of  the  Average  op  Five  Consecutive 

Readings. 


Obsenrer 

Gauge  Line. 

1 

2 

Average. 

Unit  deformation 

/  H.  F.  Moon 
\  W.  A.  BUter 

/  H.  F.  Moore 
\W.A.SUt6r 

.00000687 
.0000043 

206 
180 

.0000106 
.000014 

818 
436 

.00000873 

Stren  in  reinf oroement  in  lb.  periq.  in . 

.0000001 

262 
282 

While  these  measurements  were  not  all  on  reinforcement, 
the  probable  error  has  been  reduced  to  terms  of  stress  in  reinforce- 
ment for  convenience  of  interpretation.  It  is  very  interesting 
to  note  that  the  average  probable  error  of  =^282  lb.  per  sq.  in. 
agrees  very  weU  with  that  for  the  Turner-Carter  test  as  shown  in 
Fig.  25.  The  same  observer  took  the  data  in  both  cases,  but  the 
data  for  the  value  shown  in  Fig.  25  are  taken  directly  from  the 
records  of  the  test  and  r^resent  the  condition  on  six  typical 
gauge  lines.  The  method  of  obtaining  the  values  given  in  Table 
II  is  explained  above. 

From  the  data  in  hand  it  seems  safe  to  conclude  that  for 
ordinary  conditions  stresses  in  reuiforcement  can  be  measured  to 
the  nearest  1000  lb.  per  sq.  in.,  though  in  the  past  there  have  been 
some  glaring  failures  to  obtain  as  great  a  degree  of  accuracy  as  this. 
The  advantage  of  further  increase  in  accuracy  of  results  lies  in  the 
determination  of  the  relation  of  parts  of  the  structure. 

Effect  of  Changes  in  Temperature  on  Accuracy  of  ResvUs, — 
Changes  of  temperature  will  give  measureable  changes  of  length 
in  reinforcement,  in  concrete  and  in  instruments  made  of  ordinary 
materials.  In  most  of  the  building  tests  corrections  have  been 
made  for  the  changes  in  the  instrument  due  to  changes  in  tempera- 
ture by  means  of  observations  on  standard  unstressed  gauge 
lines  chosen  to  represent  as  nearly  as  possible  the  conditions  of 
the  reinforcement  and  the  concrete  in  the  part  of  the  structure 
tested.    The  method  of  calculating  this  correction  will  be  described 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    211 


below.  It  is  there  mentioned  that  in  distributing  the  corrections 
found  by  reference  to  the  standard  bar,  a  linear  variation  from  the 
time  of  one  standard  observation  to  the  time  of  the  next  standard 
observation  was  assumed.  Some  observations  have  been  made 
to  determine  the  correctness  of  this  assumption. 

To  determine  the  amoimt  of  change  in  length  of  an  aluminum 
extensometer  covered  and  imcovered,  a  test  was  made  in  which 
the  two  instruments  were  suddenly  exposed  to  a  change  of  tempera- 
ture of  60  deg.  F.  A  covering  which  consisted  of  a  double  layer 
of  rather  heavy  felt  protected  one  of  the  instruments  from  too  sud- 


I 


005\ 

I 


.00/ 


(a) /nstrument 

f^) /nsfrument- 
Profcctod 


FIQ,  27.- 


/O  20         30         40 

Length  of  Exposure  //?  Minutes 

-DIAGRAM   SHOWING   CHANGE   IN  LENGTH   OF   INBTRUIIENTS   DUE   TO 
CHANGE  IN  TEMPERATURE. 


den  a  change  in  temperature.  The  other  instrument  was  entirely 
unprotected.  The  results  of  this  test  are  shown  in  Fig.  27  with 
the  change  of  length  of  the  instrument  plotted  as  ordinates  against 
time  as  abscissas.  For  these  measurements  a  standard  bar  of 
Invar  steel  was  used.  The  coeflScient  of  expansion  of  this  being 
very  small,  the  change  of  length  measured  must  have  been  almost 
entirely  that  in  the  instrument.  The  curve  shows  that  for  an 
instrument  not  insulated  from  temperature  changes  only  about 
five  minutes  is  required  for  the  instrument  to  come  to  the  tempera- 
ture of  the  air.  For  the  insulated  instrument  about  20  minutes 
was  required.    This  may  be  interpreted  to  mean  that  if  an  unpro- 


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212    Slater  on  Testing  Reinforced  Concrete  Buildings. 

tected  instrument  is  used,  readings  on  the  standard  bar  should 
not  be  more  than  five  minutes  apart.  With  an  instrument  pro- 
tected as  was  this  one,  intervals  of  20  minutes  would  not  be  too 
much.  The  amount  of  change  for  the  case  shown  here  is  extreme 
as  the  instrument  was  suddenly  exposed  to  a  change  in  tempera- 
ture of  about  60  deg.  F.  This  range  would  seldom  be  found, 
and  the  length  of  time  required  to  make  the  change  for  a  smaller 
difference  of  temperature  may  be  less  but  probably  would  not 
vary  much  for  other  ranges  of  temperature.     It  may  he  concluded 


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Fia.  28. — DIAGRAM  SHOWING  CHANGE  IN  LENGTH  OF  A  STEEL  BAR  DUE  TO 
CHANGE  IN  TEMPERATURE. 

(a)  |-in.  square  bar  exposed. 
(6)  |-in.  round  bar  embedded  in  concrete. 

that  the  method  used  for  distributing  the  correction  is  justifiable, 
since  the  instrument  was  protected  from  sudden  change  of  tempera- 
ture and  the  observations  on  standard  bars  were  usually  at  inter- 
vals not  greater  than  20  minutes. 

Temperature  Effect  on  Reinforcetnent. — The  above  test  shows 
the  effect  of  change  in  temperature  on  the  instrument.  Another 
test  was  made  to  determine  the  effect  of  change  in  temperature  on 
reinforcement  imbedded  in  concrete  and  also  exposed  to  the  air. 
A  f-in.  square  bar  of  steel  entirely  unprotected  from  temperature 


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Slater  on  Testing  Reinforced  Concrete  Buildij^gs.    213 

changes  and  a  f-in.  round  bar  imbedded  in  1  in.  of  concrete  were 
exposed  to  a  sudden  change  of  temperature  of  about  43  deg.  F. 
Measurements  were  taken  on  a  6-in.  gauge  length  of  each  bar  at 
very  short  intervals  of  time.  The  results  are  shown  in  Fig.  28. 
The  results  of  this  single  test  must  be  used  with  caution  as  the 
total  measurements  were  very  small  and  a  small  error  would 
show  up  very  plainly.  However,  the  curve  for  the  imbedded  bar 
agrees  in  its  general  characteristics  with  some  of  the  results 
obtained  by  Professor  Woolson  on  '* Effect  of  Heat  on  Concrete" 
reported  in  1907.*  The  test  indicates  that  for  this  range  of  tem- 
perature rather  rapid  changes  may  be  found  in  the  reinforcement, 
corresponding  with  stresses  of  about  9000  lb.  per  sq.  in.  and  3000 
lb.  per  sq.  in.  respectively  for  exposed  reinforcement  and  that 
protected  as  in  this  case.  The  range  of  temperature  is  extreme 
and  the  size  of  bars  smaller  than  is  often  found  in  floor  con- 
struction, therefore  the  results  found  in  tests  would  probably  be 
less  extreme.  However,  this  indicates  the  necessity  of  attempting 
to  eliminate  from  the  results  of  the  test  the  effect  of  tempera- 
ture changes,  especially  if  the  stresses  measured  are  small. 

IV.    Records  and  Calculations. 

Since  the  beginning  of  the  use  of  the  Berry  extensometer 
for  testing  purposes,  as  much  development  has  been  made  in  the 
keeping  of  notes  as  in  the  use  of  the  instrument.  Because  of  a 
lack  of  completeness  of  notes  the  advantages  of  the  use  of  the 
standard  bar  were  not  fully  realized  for  some  time.  Only  after 
the  method  of  keeping  notes  had  been  highly  systematized  was 
it  possible  to  properly  make  the  corrections  which  observations 
on  the  standard  bars  indicated-  should  be  made.  During  the 
time  of  placing  an  increment  of  load  the  recorder  will  have  con- 
siderable time  in  which  to  be  working  up  results  of  the  series  of 
observations  taken  at  the  previous  increment  of  load,  and  as  the 
method  of  making  these  calculations  is  quite  intricate,  a  man  is 
required  for  this  work  who  has  ability  to  do  more  than  merely 
record.  It  is  important  that  calculations  should  be  kept  up  as 
the  work  progresses,  because  it  can  be  done  with  less  labor  then 
than  at  any  other  time  and  because  it  will  be  of  value  to  know 
as  the  test  progresses  what  results  are  being  secured. 

•  See  Proceedtnga,  Vol.  VII.  Am.  Soc.  for  Test.  Mala. 


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214    Sla-bpr  on  Testing  Reinforced  Concrete  Buildings. 

RECORDS. 

It  is  very  important  on  account  of  the  great  number  of 
observations  taken  (about  12,000  in  the  Turner-Carter  test) 
that  all  records  be  arranged  systematically.  The  following 
points  are  mentioned  as  being  important  in  this  connection, 
(a)  In  the  field  test  individual  readings  should  be  recorded  and 
their  average  used  as  a  single  observation.  The  proposed  abridg- 
ment of  this  procedure  (see  p.  204)  should  be  considered  as  a  sug- 
gestion for  later  development.  (6)  Recording  readings  in  the 
order  of  their  size  will  assist  the  recorder  in  obtaining  the  correct 
readings  and  in  rapidly  obtaining  the  average,  (c)  The  exact 
sequence  of  observations  should  be  maintained  in  the  records 
as  the  calculation  of  corrections  depends  largely  on  this. 

Fig.  29  shows  a  form  for  the  recording  of  original  readings 
and  the  results  calculated  from  them. 

calculations. 

The  calculations  of  corrections  and  applying  them  to  the 
results  makes  the  reduction  of  data  rather  intricate.  This  work 
has  been  reduced  to  a  definite  form  shown  in  Fig.  30.  In  this 
form  the  zero  length  of  instrument  (see  definition,  p.  172)  is  assumed 
as  correct  and  is  used  as  a  standard  of  reference.  The  correc- 
tions are  distributed  among  the  gauge  lines  as  though  the  change 
in  the  length  were  a  linear  function  of  the  time  from  one  standard 
bar  observation  to  the  next  one.  These  assumptions  do  not 
entirely  accord  with  the  facts  but  have  been  satisfactory  as  a 
working  basis.  Any  other  standard  bar  observation  than  the 
zero  length  would  do  as  well  for  a  standard  of  reference  except 
for  matters  of  convenience. 

V.    Cost  of  the  Tests. 

An  attempt  was  made  to  get  information  by  which  the  cost 
of  the  tests  could  be  estimated,  but  it  is  found  that  from  the 
data  on  hand  no  finely  drawn  conclusions  are  warranted.  The 
costs  of  the  tests  enumerated  here  range  from  about  $50  to  as 
much  as  $2000,  depending  on  the  nature  of  the  test  and  the  expenses 
for  railroad  fare,  hotel  bills  and  pay  for  expert  assistance.  In 
the  case  of  $50  the  cost  is  only  that  in  excess  of  what  would  have 


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Slater  on  Testing  Reinforced  Concrete  Buildinos.    215 


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216     Slater  on  Testing  Reinforced  Concrete  Buildings. 


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Slater  on  Testing  Reinforced  Concrete  Buildings.    217 

been  necessary  for  the  acceptance  test  of  a  building.  It  does 
not  include  the  salaries  of  the  testing  engineers  and  as  there  were 
no  hotel  expenses  this  cost  is  perhaps  $150  less  than  what  could 
be  ordinarily  expected  for  such  a  test.  The  data  in  hand  indi- 
cate that  a  test  as  extensive  as  several  in  this  series  have  been 
would  be  likely  to  cost  from  $1500  to  $2000^  but  that  one  of  the 
type  represented  by  the  Carleton  test  may  be  made  at  an  expense 
slightly  above  that  of  the  acceptance  test  so  frequently  required. 

For  a  very  slight  additional  cost,  measurements  of  stresses 
in  a  building  floor  may  be  made  at  points  of  especial  interest 
during  the  progress  of  the  load  test  which  is  often  required  as  a 
condition  of  acceptance. 

The  stage  has  been  reached  in  the  investigation  of  reinforced 
concrete  where  building  tests  may  be  expected  to  contribute 
information  of  great  value  to  the  designer  and  builder  in  rein- 
forced concrete.  The  main  feature  of  such  tests  should  be  the 
measurement  of  stresses,  but  information  as  to  the  location  and 
size  of  cracks  will  be  of  great  value  in  checking  the  results  if  the 
examination  for  cracks  is  conducted  with  sufficient  care  and 
minuteness.  There  is  need  for  increasing  as  much  as  possible 
the  accuracy  of  deformation  measurements  and  experience  in  the 
use  of  the  instrument  is  gradually  accomplishing  this.  All  the 
confirmatory  evidence  possible  on  the  correctness  of  results  should 
be  obtained. 


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THE  DESIGN  OF  CONCRETE  FLAT  SLABS.* 

By  F.   J.   TRELEASE.f 

The  rapid  introduction  and  development  of  flat  slab  floors 
of  reinforced  concrete  is  sufficient  evidence  of  the  great  importance 
of  this  type  of  construction.  In  fact,  the  demands  of  owners 
and  builders  for  flat  slabs  are  so  insistent,  that  in  spite  of  the  lack 
of  reliable  methods  of  design,  many  acres  of  such  floors  are  built 
every  year.  The  insistence  of  this  demand  has  led  many  engineers 
to  advance  theories  of  the  structural  action  of  flat  slabs,  and  these 
theories  yield  perhaps  the  most  striking  contrasts  and  disagree- 
ments to  be  found  in  modem  engineering  practice.  The  reason 
for  thib  is  largely  because  the  flat  slab  is  an  extreme  example  of  a 
redundant  structure,  and  its  mathematical  analysis  has  so  far 
been  based  upon  certain  arbitrary  assumptions  which  vary  in  the 
different  analyses.  The  differences  in  these  assmnptions  are  so 
great  that  the  practical  application  of  the  theories  founded  upon 
them  to  flat  slabs  of  reinforced  concrete  yield  results  varying  by 
about  four  hundred  per  cent.  This  variation  leads  one  to  class 
the  flat  slab  as  beyond  the  range  of  pure  analysis  and  one  must 
look  to  experimental  engineering  for  a  satisfactory  solution  of  the 
problem. 

The  usual  load  tests  of  completed  structiu*es  may  be  dismissed 
at  once  as  being  entirely  inadequate  as  a  basis  of  design.  In  such 
tests  usually  but  one  panel  of  a  structure  is  loaded,  which  does  not 
give  maximum  stress  conditions  in  a  flat  slab  floor.  Even  if  several 
panels  be  loaded  and  the  test  carried  to  destruction  it  will  at  best 
only  roughly  indicate  the  stresses  at  the  weakest  point  of  the 
structure  under  the  scheme  of  loading  employed  and  cannot  give 
any  information  as  to  the  economy  of  the  design. 

A  very  recent  and  more  adequate  form  of  test  on  completed 
structures  is  that  in  which  several  panels  of  a  building  are  loaded, 
not  necessarily  to  destruction,  and  in  which  the  actual  elastic 
deformations  of  both  reinforcement  and  concrete  are  measured 


*  Advance  Review  of  a  Thesis  presented  to  Washington  University  for  the  degree  of  Civil 
Engineer. 

t  Engineer,  Corrugated  Bar  Company,  Buffalo.  N.  Y« 

(218) 


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Trelease  on  Design  of  Concrete  Flat  Slabs.      219 

by  extensometers.  The  results  obtained  in  such  a  test  would 
form  a  satisfactory  basis  for  the  design  of  similar  structures  if  one 
could  eliminate  from  the  results  the  effects  of  tension  in  the  con- 
crete, arch  action,  annular  slab  action  and  many  other  indeter- 
minate factors,  which  enter  largely  into  all  tests  of  reinforced 
concrete.  These  effects  are  so  indeterminate  that  they  cannot 
be  satisfactorily  eliminated,  thus  rendering  results  of  tests  on 
completed  structures  more  or  less  imsatisfactory  as  a  basis  of 
design.  The  average  engineer  hesitates  to  coimt  on  these  factors 
in  designing  and  even  if  he  had  no  personal  objections  to  their 
use,  none  of  the  building  laws  or  regulations  will  permit  of  any 
allowance  being  made  for  them. 

It  would  seem,  then,  that  for  satisfactory  solution  of  the 
problem  there  must  be  obtained  an  empirical  analysis  of  the  struc- 
tural action  of  flat  plates  derived  from  experiments  on  plates 
of  homogeneous  material. 

Such  an  analysis  could  be  then  used  in  the  design  of  flat  slabs 
of  reinforced  concrete,  using  any  desired  combination  of  unit 
stresses  ^nd  making  such  allowances  for  tension  in  the  concrete, 
etc.,  that  personal  judgment  or  various  building  regulations  might 
dictate. 

It  is  the  purpose  of  this  paper  to  describe  and  give  the  results 
of  such  an  empirical  analysis  based  on  experiments  conducted 
by  the  author  in  the  Research  Department  of  the  Corrugated 
Bar  Company,  under  the  general  direction  of  Mr.  A.  E.  Lindau, 
Chief  Engineer.  This  work  was  started  early  in  1910,  and  has 
continued  almost  iminterruptedly  to  the  present  time. 

A  very  interesting  and  exceedingly  simple  little  experiment 
was  made  on  a  sheet  of  heavy  cardboard  fastened  over  twelve 
spools  representing  columns.  By  pressing  the  fingers  on  this 
little  model  at  various  points  much  was  learned  as  to  the  general 
action  of  flat  plates.  For  instance,  one  could  press  upon  the  center 
of  several  panels  and  note  that  the  surface  of  the  model  was  convex 
upwards  at  right  angles  to  the  lines  joining  the  columns  and  form- 
ing the  sides  of  the  panels,  showing  that  tension  in  the  top  face 
existed  at  that  point,  although  none  of  the  systems  of  reinforce- 
ment then  in  use  provided  resistance  to  these  stresses. 

The  work  most  productive  of  results  was  a  series  of  experi- 
ments on  rubber  models  of  flat  slab  floors.     Rubber  was  chosen 


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220      Treleasb  on  Design  op  Concrete  Flat  Slabs. 

for  the  models  as  best  fulfilling  the  requirements  of  reasonable 
homogeneity,  low  modulus  of  elasticity,  and  the  ease  with  which 
all  its  physical  properties  could  be  determined  in  the  laboratory. 
The  models  used  consisted  essentially  of  a  plate  of  pure  gum  rub- 
ber, fixed  so  as  to  form  the  top  of  an  air-tight  box  containing  the 
proper  number  of  1 J  in.  round  columns  to  divide  it  into  nine  panels, 
each  8  in.  square. 

The  method  adopted  for  applying  load  to  the  model  was 
rather  unique  and  extremely  satisfactory,  as  it  not  only  permitted 
the  intensity  of  the  load  to  be  easily  and  accurately  read,  but 


FIG.  1. — BOX  AND  ABPIRATOR  FOR  RUBBER  MODEL  OF  FLAT  SLAB  FLOOR. 

insured  absolute  uniformity  of  distribution,  and  at  the  same  time 
left  the  entire  upper  surface  of  the  slab  unobstructed  and  free 
for  observations  and  measurements.  A  partial  vacuum  was 
formed  in  the  box,  thus  obtaining  on  the  face  of  the  plate  the  pres- 
sure of  the  atmosphere  which  was  read  by  a  simple  U-tube  manom- 
eter.    The  box  and  aspirator  are  shown  in  Fig.  1. 

In  the  first  series  of  experiments  the  rubber  plate  used  was 
0.34  in.  thick.  A  stress  strain  diagram  obtained  from  a  strip 
cut  from  this  plate  is  shown  in  Fig.  2.  At  first  the  scope  of  \his 
series  was  limited  to  the  measurement  of  the  shape  of  the  elastic 
surface  of  the  plate  under  stress.    With  this  end  in  view,  deflection 


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Trblease  on  Design  of  Concrete  Flat  Slabs. 


221 


readings  were  taken  at  numerous  points  in  the  various  panels. 
In  some  cases  these  were  taken  at  points  only  one-twentieth  of 
the  span  apart. 

The  values  of  these  readings  were  then  averaged,  grouping 
those  which  through  symmetry  should  be  alike,  and  the  results 
plotted.     Equi-deflection  lines  were  then  drawn,  giving  contour 


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FIG.  2. — STRESS  STRAIN  DIAGRAM   FOR  RUBBER. 


maps  of  the  surface.  Fig.  3  shows  such  a  map  for  one-quarter 
of  the  model,  while  Fig.  4  shows  the  lines  of  equi-deflection  for 
the  central  panel.  The  approximate  location  of  the  lines  of 
inflection  for  imaginary  beams  radiating  from  the  column  center 
have  been  plotted  in  Fig.  5. 

Many  interesting  conclusions  can  be  drawn  from  the  deflection 
maps.    They  show  at  once  the  general  nature  and  intensity  of  the 


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222       Trelease  on  Design  op  Concrete  Flat  Slabs. 

stresses  existing  in  the  plate.  They  show  beyond  doubt  that 
tension  exists  in  the  upper  face  of  the  slab  at  right  angles  to  the 
lines  joining  the  columns  and  forming  the  sides  of  the  panel,  being 
a  maximum  at  the  colunms  and  decreasing  to  a  minimum  at  the 
mid-point,  although  even  this  minimum  value  of  the  tension  in  the 
top  face  is  approximately  equal  to  the  tension  in  the  bottom  face 
at  the  center  of  the  panel.  Inspection  of  Fig.  6  will  make  this 
more  clear.     The  top  curve  is  a  section  along  the  side  of  a  panel 


WQ.   3. — CONTOUR  MAP  OP  ONE-FOURTH  OF  MODEL. 

and  the  lower  curve  a  section  through  the  middle  of  the  panel 
parallel  to  one  side.  From  the  radii  of  curvature  of  these  curves, 
it  will  be  seen  that  the  maximum  stress  at  the  side  occurs  over  the 
colmnn,  while  the  section  through  the  middle  shows  that  the  stress 
is  of  practically  equal  intensity  at  the  center  of  the  panel  and  at 
the  mid-point  of  the  panel  edge.  Tension  in  the  top  surface 
at  the  edge  of  the  panel  has  never  been  provided  for  in  the  rein- 
forcing of  flat  slabs,  although  the  need  for  it  has  been  clearly 
pointed  out  time  and  again  by  the  formation  of  cracks  in  the 


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Tbblease  on  Design  of  Concbete  Flat  Slabs.       223 


FIG.   4. — CONTOUR  MAP  OF  INTERIOR  PANEL. 


FIG.   5. — USE  OF  INFLECTION  FOR  IMAGINARY  RADIAL  BEAMS. 


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224      Trelease  on  Design  of  Concrete  Flat  Slabs. 

concrete.  These  cracks,  which  run  from  column  to  cokmm 
along  the  sides  of  the  panel,  have  formed  in  nearly  every  multiple 
panel  load-test  of  a  reinforced  concrete  flat  slab  which  has  been 
made,  and  have  even  formed  in  several  floors  under  their  dead 
weight  only.  It  was  hoped  that  the  radii  of  curvature  of  the 
elastic  surface  could  be  accurately  measured  and  the  bending 
moments  deduced  from  them.  It  was  foimd,  however,  that 
results  so  obtained  were  too  indefinite  to  be  considered  reliable. 
It  was  evident  that  to  obtain  exact  information  as  to  the 
distribution  and  magnitude  of  stresses  existing  in  the  plate,  it 


5ecf^/o/7  a^  ^  of  Co/(//7?/?^. 


^ecf/on  fhroi/^^  d  of  Panel 

FIG.  6. — SECTIONS  AT  EDGE  AND  CENTER  OP  INTERIOR  PANEL. 

would  be  necessary  to  measure  the  actual  elastic  deformation  of 
the  material  caused  by  these  stresses.  This  was  attempted  in 
many  ways;  by  measuring  distortion  of  squares  ruled  on  the 
slab;  by  measuring  cracks  formed  in  plaster  of  paris  coatings  and 
lines,  and  by  various  forms  of  extensometers.  After  trying  many 
devices,  it  was  decided  to  use  a  microscope  fitted  with  an  ocular 
micrometer  and  to  measure  with  it  the  deformations  occurring 
over  a  gauge  length  0.5  in.  long.  The  ocular  micrometer  is  a 
disc  of  glass,  engraved  with  a  fine  scale,  which  is  inserted  in  the  eye 
piece.  The  disc  lies  in  the  plane  of  the  image  formed  so  that  the 
engraved  lines  appear  to  be  upon  the  image  itself,  and  its  length 


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Trelease  on  Design  of  Concrete  Flat  Slabs.      225 


( 

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ria.   7. — MODEL  AND  EXTEN80METERS. 


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226      Tbelease  on  Design  of  Concrete  Flat  Slabs. 

can  be  easily  read.  The  absolute  value  of  one  division  of  the  scale 
depends  upon  the  magnification  used,  and  was  approximately 
0.00048  in.  in  these  experiments.  The  total  field  was  about  one- 
fortieth  of  an  inch. 

Several  devices  were  tried  for  bringing  the  deformations 
occurring  over  the  gauge  length  into  the  field  of  the  micrometer. 
At  first  a  strip  of  heavy  tinfoil  was  fastened  at  each  end  of  the 
gauge  length  by  passing  a  fine  needle  through  it  into  the  rubber. 
The  pointed  ends  of  these  strips  nearly  touched  at  the  middle  of 
the  gauge  length  and  the  distance  between  them  was  measured 
under  no  load,  and  again  imder  the  various  loads  employed.  This 
arrangement  of  tinfoil  strips  was  not  satisfactory,  as  readings 
taken  with  it  were  not  consistent  with  each  other,  caused  probably 
by  slight  play  of  the  strips  around  the  needles,  or,  perhaps,  by 
the  strips  themselves  buckling  as  the  gauge  length  shortened. 

After  many  trials,  the  following  method  was  adopted  and 
foimd  entirely  satisfactory.  A  small  piece  of  very  fine  needle 
was  placed  point  up  in  the  rubber  at  one  end  of  the  gauge  length 
and  at  the  other  end  was  placed,  point  down,  a  piece  of  needle 
with  the  exposed  end  ground  to  a  triangular  shape  and  highly 
polished.  A  small  strip  of  brass  was  gfoimd  to  a  knife  edge  at  one 
end,  and  at  the  other  a  small  conical  depression  was  made.  The 
point  of  the  first  needle  entered  this  depression,  and  the  knife 
edge  was  very  close  to  the  triangular  end  of  the  other  needle. 
The  distance  from  the  end  of  the  strip  to  one  point  of  the  triangle 
was  read  very  easily,  and  the  arrangement  gave  per^pct  satisfac- 
tion. Fig.  7  shows  a  general  and  a  detail  view  of  the  extensometers 
in  place. 

In  this  first  series,  these  extensometers  were  arranged  on 
lines  radiating  from  the  columns  so  that  the  readings  both  along 
the  lines  and  perpendicular  to  them  were  obtained.  Full  results 
of  these  readings  are  not  given,  because  it  was  found  that  the 
deformation  at  a  given  point  increased  more  rapidly  than  the 
loads,  indicating  catenary  action  or  pure  tension  throughout  the 
cross-section  of  the  plate.  If  such  action  existed,  the  tensile 
deformations  read  in  the  top  fibers  of  the  plate  would  be  higher 
than  the  true  values  caused  by  bending  alone  and  likewise  the 
compressive  deformations  of  the  top  fibers  would  be  less  than  they 
should  be.    To  test  for  this,  short  colmnns  were  clamped  on  the 


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Trelease  on  Design  of  Concrete  Flat  Slabs.      227 

top  of  the  slab  directly  over  those  on  the  under  side  and  the  load 
reversed.  Zero  readings  for  the  reversed  load  were  taken  under  a 
pressure  equaling  the  dead  weight  of  the  slab.  Fig.  8  shows  read- 
ings obtained  in  this  way  and  under  direct  load,  for  points  along 
the  line  forming  the  side  of  the  panel.  The  values  of  the  deforma- 
tion due  to  bending  moment  alone  are  the  arithmetical  averages 
of  the  direct  and  reversed  readings,  and  the  true  zero  line  has  been 


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FIQ.   8. — DEFORMATIONS  UNDER  DIRECT  AND  REVERSED  LOADS. 

plotted  showing  the  amount  of  catenary  action  existing.  This 
method  of  load  reversal  was  too  tedious  to  be  adopted  and  it  was 
decided  to  use  a  thicker  plate  in  the  next  series  of  experiments. 

The  results  obtained  in  the  first  series  of  experiments  have 
been  discarded  in  favor  of  those  in  the  second  series  and  the  first 
series  has  been  regarded  as  merely  preliminary  and  as  having 
served  its  purpose  in  enabling  the  many  mechanical  difficulties 
to  be  overcome  and  in  indicating  many  points  to  be  covered. 


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228      Trelease  on  Design  of  Concbbte  Flat  Slabs. 

In  the  second  series  of  tests  the  apparatus  used  was  the  same 
as  that  employed  in  the  first  series,  except  that  the  rubber  plate 
was  0.485  in.  think.  This  greater  thickness  was  used  because 
it  was  thought  that  the  effect  of  catenary  action  would  be  less 
on  a  heavy  plate  than  the  lighter  one  used  in  the  first  series.  The 
correctness  of  this  assumption  was  later  proved  by  a  series  of 
readings  of  deformations  at  various  points  under  direct  loads 


6      3     /o    /jt    /^    /3    /a     2o    rz    ^ 

FIG.  9. — propobhonalitt  of  btress  to  load  for  second  model. 

equivalent  to  from  1  to  6  in.  of  water  which  showed  proportion- 
ality of  deformation  to  load.  The  results  of  these  readings  are 
plotted  in  Fig.  9.  The  lack  of  catenary  action  was  also  confirmed 
by  reversing  the  load  and  obtaining  curves  identical  to  those 
obtained  under  direct  load. 

Deflection  readings  were  taken  at  points  over  the  interior 
panel  spaced  one-tenth  of  the  span  apart.  Fig.  10  is  a  plan  of 
the  interior  panel  upon  which  have  been  plotted  contour  lines 


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FIG.   10. — CONTOUR  MAP  OP  INTERIOB  PANEL. 


FEG.    11. — UKEB  OF  INFLECTION  FOB  STRIPS  PARALLEL  TO  SIDES  OF  PANEL. 


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230      Trelease  on  Design  of  Concrete  Flat  Slabs. 

representing  elastic  deflections  of  0.01  in.  caused  by  a  load  equiva- 
lent to  5  in.  of  water.  Sections  of  the  surface  so  defined  were 
taken  parallel  to  the  sides  of  the  panel  and  the  points  of  inflec- 
tion plotted  in  Fig.  11.  The  lines  joining  these  are  lines  of  inflec- 
tion for  imaginary  beams  or  strips  parallel  to  the  sides  of  the 
panel.  These  lines  agree  very  well  with  the  results  obtained 
later  from  deformation  readings. 

Fig.  12  is  an  exaggerated  sketch  of  the  elastic  surface  upon 
which  have  been  marked  coefficients  for  deflection.  To  apply 
these  to  concrete  flat  slabs  reinforced  parallel  to  the  sides  of  the 
panels  a  strip  of  unit  width  is  assumed  along  the  edge  of  the  panel, 


FIG.    12. — DIAGRAM   OF  ELASTIC   SURFACE   AND   DEFLECTION   COEFFICIENTS 

and  another  at  right  angles  to  this  along  the  center  line  of  the 
panel.  Knowing  the  total  load  per  square  foot  on  the  panel, 
as  well  as  the  eflfective  depths  and  steel  percentages  of  each  strip, 
it  is  an  easy  matter  to  obtain  the  deflections.  Instead  of  work- 
ing out  the  values  of  the  moment  of  inertia  of  the  strips  one  may 
follow  the  method  outHned  by  Mr.  Eli  White  in  the  Engineering 
Record  of  November  9,  1907,  and  elaborate<l  by  Mr.  G.  F.  Dodge 
in  his  Diagrams  for  Designing  Reinforced  Concrete  Structures. 
To  simplify  the  computations  the  strips  may  first  be  treated  as 
simply  supported  beams,  and  the  deflections  so  obtained  multiplied 
by  the  ratio  of  the  deflection  coefficients. 

The  results  of  the  first  series  of  tests  indicated  that  tensile 
reinforcement  would  have  to  be  provided  in  the  top  of  the  slab 


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Trelease  on  Design  of  Concrete  Flat  Slabs.      231 


at  right  angles  to  the  lines  fonning  the  sides  of  the  panel,  and 
it  was  decided  that  a  two-way  system  of  reinforcement  would  be 
most  adequate,  both  in  providing  this  reinforcement  and  in  tak- 
ing care  of  the  stresses  existing  in  other  parts  of  the  construction, 
and  consequently  the  arrangement  of  the  extensometers  was  as 
shown  in  Fig.  13.     It  will  be  seen  from  this  figure  that  deforma- 


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PIG.    13. — ARRANGEMENT  OF  EXTENSOMETERS 


tions  were  read  parallel  to  each  side  of  the  panel  at  points  spaced 
one-eighth  of  the  span  apart,  and  so  distributed  that  deformations 
in  other  portions  of  the  plate  were  by  the  symmetry  of  the  con- 
struction obtained  from  readings  on  these. 

It  was  found  that  a  load  equivalent  to  5  in.  of  water  gave 
deformations  large  enough  to  be  easily  read,  and  this  load  was 
therefore  adopted.     The  extensometers  at  all  the  points  were 


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232      Trelease  on  Design  of  Concrete  Flat  Slabs. 


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Trelease  on  Design  of  Concrete  Flat  Slabs.      233 


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FIG.   15. — ^DISTRIBUTION  CURVES. 


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234      Tkeleasb  on  Design  op  Concrete  Flat  Slabs. 

read  under  no  load,  and  again,  under  load;  the  differences  giving 
the  elastic  deformations  caused  by  the  load.  The  load  was 
applied  and  released  time  and  again,  as  many  as  forty  readings 
being  taken  on  some  of  the  critical  points  by  each  of  two  observers. 
The  readings  obtained  at  any  given  point  agreed  with  one  another 
to  within  a  very  few  divisions  of  the  micrometer.  Table  I  gives 
the  averages  of  all  the  readings  taken.  It  will  be  seen  upon  inspec- 
tion of  Fig.  13  that  two  sets  of  curves  may  be  plotted  from  these 
readings.  One  set  will  show  moment  diagrams  for  imaginary 
strips,  the  axes  of  which  lie  along  the  zero  lines  of  the  curves. 
Curves  of  the  other  set  show  the  distribution  of  moment  among 
various  strips  of  this  kind.     Since  a  two-way  system  of  reinforce- 


Table  I. — Averages  of  Deformation  Readings. 

Point. 
Line. 

Bos. 

A 

A 

C.  L.  of 
Exterior 
Panel. 

A. 

Tane 

of 
ColB. 

pI 

A. 

A 

C.  L.  of 
Interior 
Panel. 

A 

B 
C 
D 

e 

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I 
K 
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18.8 

9.17 
14.0 

6.6 

0.0 
4.5 

-2.26 

0 

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-2.0 
-0.83 
-0.67 

-1.83 

-6.0 

-0.5 
-6.5 
-4.1 
-3.0 

0.5 

-1.0 

-3.0 

-1.17 

-0.25 

-1.67 

-0.6 

3.82 

6.5 

0.33 

17.33 

21.25 

10.33 

2.54 

2.0 

2.67 
4.25 
6.33 
7.0 
10.61 

6.0 

0.5 
-0.5 
-0.25 
-1.0 
-4.0 
0 
-0.6 
-1.33 

-3.0 

-3.76 

-4.75 

-«.o 

-8.0 

-4.03 
-5.6 
-6.0 
-10.0 
-0.66 
-7.6 
-3.33 
-2.0 
-0.75 

ment  was  to  be  used,  it  was  decided  to  design  each  set  of  bars 
independently.  For  square  panels  the  reinforcement  would,  of 
course,  be  the  same  in  each  direction. 

Fig.  14  shows  the  moment  curves  for  strips  parallel  to  one 
side  of  the  panels,  while  Fig.  15  shows  distribution  curves  for 
these  same  strips.  These  two  sets  of  curves  can  be  combined  to 
form  a  surface  showing  both  moments  and  distribution  for  one 
set  of  strips.  A  photograph  of  this  surface  for  four  panels  in  one 
comer  of  the  model  is  shown  in  Fig.  16. 

Fig.  17  is  a  sketch  showing  the  surface  for  the  interior  panel. 
In  this  figure  the  ordinates  from  the  plane  A-B-C  to  the  surface 
are  proportional  to  the  deformations  of  the  top  fiber  of  the  plate 
parallel  to  side  B-C  at  the  point  at  which  the  ordinate  intersects 
the  surface.     Sections  parallel  to  B-C  will  be  the  moment  dia- 


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Tbelease  on  Design  of  Concrete  Flat  Slabs.      235 

grams  similar  to  those  in  Fig.  14,  and  sections  parallel  to  A-B 
will  be  distribution  curves  similar  to  those  shown  in  Fig.  15. 

In  Figs.  14  and  15  the  ordinates  to  the  ciu^es  are  shown  in 
terms  of  divisions  of  the  micrometer.  In  order  to  co-ordinate 
divisions  of  the  micrometer  with  bending  moment,  a  strip  of  the 
rubber  was  cut  from  the  plate,  and  the  stress  strain  diagram  shown 
in  Fig.  18  obtained.  Both  the  axial  and  lateral  deformations  of 
the  strip  were  measured,  from  which  the  modulus  of  elasticity 
was  found  to  be  about  1,000  and  Poisson's  ratio  about  .44;  one 


FIG.    16. — MOMENT    SURFACE    FORMED    BY    COMBINING     MOMENT     CURVES    AND 
DISTRIBUTION  CURVES. 

division  of  the  micrometer  corresponding  to  a  unit  elongation  of 
0.001. 

The  value  of  one  division  of  the  micrometer  in  terms  of 
bending  moment  was,  however,  obtained  directly  in  the  follow- 
ing manner: 

A  strip  of  rubber  cut  from  the  plate  was  supported  over  two 
knife  edges,  and  loaded  as  shown  in  Fig.  19.  An  extensometer 
exactly  like  those  used  on  the  plate  was  placed  on  top  of  the  strip 
between  the  supports.  Known  weights  were  applied,  and  the 
accompanying  deformations  read.  Fig.  19  shows  deformations 
so  obtained,  plotted  against  bending  moments  in  in.-lb.  per  inch 


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236      Trelease  on  Design  of  Concrete  Flat  Slabs. 

width  of  strip.  From  this  curve  the  moment  equivalent  of  any 
number  of  divisions  of  the  micrometer  can  be  obtained.  The 
unit  load  on  the  panel  being  known^  together  with  the  span, 
what  might  be  termed  the  "gross  bending  moment"  or  M=wS^, 
may  be  obtained.  In  this  case  the  clear  span  S  was  6.75  in.  and 
the  load  equivalent  to  5  in.  of  water,  or  .1808  lb.  per  sq.  in.,  so 
that  M=wS^  =  8.2377  in.-lb.  If  the  net  moment  at  any  point 
be  ilf  ==  wS^/z,  the  value  of  the  z  may  be  obtained  from  the  moment 
curveB  in  Fig.  14  and  the  calibration  curve  in  Fig.  19.     With  S 


FIQ.     17. — ^DIAGRAM    OF    MOMENT    BURFACB    FOR    CONTtNUOUB    FLAT    PLATS 
SUPPORTED  AT  CORNERS. 

equal  to  the  clear  span  from  edge  to  edge  of  column  heads,  z  » 
215/D,  where  D  is  the  ordinate  to  the  moment  curves  in  divisions 
of  the  micrometer. 

On  Fig.  20  the  moment  expressions  obtained  in  the  above 
manner  have  been  marked  at  the  critical  points. 

Having  now  obtained  an  empirical  analysis  of  a  homogeneous 
plate  it  will  be  applied  to  flat  slabs  of  reinforced  concrete.  This 
may  be  done  without  hesitation  because  the  whole  history  of  the 
development  of  reinforced  concrete  has  been  along  such  lines. 
It  was  found  that  once  having  solved  the  problem  of  internal 


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Tbelease  on  Design  op  Concketb  Flat  Slabs.      237 

stress  distribution  in  a  concrete  beam,  there  could  be  safely- 
used  the  equations  for  external  moments  applying  to  homogeneous 
beams,  and  so  on. 

In  this  empirical  analysis  the  components  in  two  directions 
of  the  stresses  existing  in  a  homogeneous  plate  have  been  measured 
and  reinforcement  will  be  supplied  in  the  concrete  flat  slab  to 
resist  these  components  where  they  show  tensile  stresses.     In 


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^/i^/j/o/fj   o/'  Af/cra/7?efer 

FROM    PLATE  LOADED  FOB  MOMENT   CALIBRATION   OF   BXTEN- 
80METEB8. 


laying  out  the  reinforcement  a  departure  is  made  from  the  old 
diagonal  or  four-way  system  and  the  two-way  system,  Fig.  21, 
employed. 

One  of  the  greatest  advantages  of  the  two-way  system  is 
the  location  of  tensile  reinforcement  in  the  top  of  the  slab  between 
the  columns,  which  tends  to  prevent  the  formation  of  cracks 
extending  from  column  to  column  and  stiffens  the  whole  struc- 
ture,  giving   all   the   advantages   of   continuous    construction. 


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238      Tbelease  on  Design  op  Concrete  Flat  Slabs. 

Another  point  is  that  the  tensile  reinforcement  over  the  columns 
is  in  but  two  layers  and  hence  the  effective  depth  at  this  critical 
point  is  much  greater  than  would  be  possible  with  the  systems 
in  which  four  or  more  layers  are  used. 


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FIQ.    19. — MOMENT  CALIBRATION  CURVE   FOR   EXTENSOMETER. 

The  ideal  reinforcement  would  be  such  that  its  area  at  any 
point  be  directly  proportional  to  the  ordinate  of  the  moment 
surface  shown  in  Fig.  17,  but  such  reinforcement  is  obviously 
impossible  in  practice.  The  panel  is,  therefore,  assumed  to  be 
divided  into  ten  strips  or  imaginary  beams,  five  parallel  to  each 


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Tbelease  on  Design  of  Concrete  Flat  Slabs.      239 

side,  and  such  moments  assumed  for  their  design  as  will  give 
reinforcement  areas  conforming  most  closely  to  the  theoretical 
values. 

The  widths  of  these  imaginary  beams  together  with  the 
moment  factors  applying  to  each  are  shown  in  Fig.  22.  ^  To 
avoid  confusion  in  the  drawing,  the  widths  and  moments  for  but 


FIG.   20. — ^MOMENTS  PER  UNIT  WU>TH  DERIVED  FROM  EXPERIlfENTB. 

one  set  of  strips  are  shown,  those  for  the  other  set  being  the  same 
but  turned  through  ninety  degrees.  The  numbers  in  the  circles 
on  the  diagrams  are  moment  coefficients  entering  into  the  denomi- 
nator of  the  moment  equation.  Thus,  the  moment  at  the  center 
of  the  panel  in  the  middle  strip  or  beam  is  Af  =  i6JjSV40,  where 
w  is  the  total  unit  live  and  dead  load  on  the  panel  in  lb.  per  sq.  ft., 
«  is  the  clear  span  in  feet,  and  the  40  is  the  moment  coefficient 


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240   Trelease  on  Design  op  Concrete  Flat  Slabs. 


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Trelease  on  Design  op  Concrete  Flat  Slabs       241 

shown  in  the  circle  at  this  point.  M  is  the  bending  moment  in 
ft.-lb.  per  ft.  of  width,  and  is  positive,  requiring  reinforcement 
in  the  bottom  of  the  slab,  as  indicated  by  the  fact  that  the  arrow 
showing  the  direction  of  the  reinforcement  is  dashed.  The 
moments  of  other  points  of  the  panel  are  obtained  in  the  same 
manner.  The  sections,  at  the  bottom  of  Fig.  22  show  how  the 
theoretical  distribution  curves  are  replaced  by  more  practical 
stepped  lines.  In  making  this  change  an  excess  of  reinforcement 
has  been  introduced  at  the  center  of  the  strips  to  provide  for 
single  panel  concentrations  of  loading. 

Since  the  maximum  stresses  in  a  flat  slab  occur  at. the  col- 
umns, the  use  of  a  slab  of  uniform  thickness  is  wasteful  of  concrete 
and  adds  mmecessary  dead  load.  The  imnecessary  concrete 
can  be  done  away  with,  decreasing  the  weight  and  cost  of  the 
structure  and  at  the  same  time  adding  to  its  efficiency,  if  a  rec- 
tangular cap  of  concrete  is  left  over  the  columns,  extending  to 
about  the  fifth  point  of  the  span. 

The  general  method  of  procedure  in  designing  a  concrete 
flat  slab  in  accordance  with  this  method  is  to  first  find  the  areas 
of  reinforcement  required  in  the  different  bands  at  the  center 
line  of  the  panel.  These  areas  are  supplied  by  rods  of  the  proper 
size  and  spacing,  every  other  one  of  which  is  bent  up  in  the  top 
at  about  the  quarter  point  and  extends  over  into  the  adjacent 
panels,  while  the  remainder  are  straight  and  extend  about  6  in. 
past  the  edge  of  the  panel.  This  arrangement  gives  the  necessary 
amounts  of  reinforcement  in  both  the  top  and  bottom  of  the  slab, 
except  in  the  areas  over  the  columns  where  the  necessary  extra 
reinforcement  in  the  top  is  supplied  in  the  form  of  short,  straight 
bars,  remembering  that  at  these  points  the  effective  depth  of  the 
slab  is  increased.  To  avoid  bimching  the  bars  in  the  top  of  the 
dab,  a  bent  bar  in  one  panel  should  be  in  line  with  a  straight 
bar  from  the  next  panel. 

The  line  of  inflection  may  be  safely  taken  at  the  fifth  point 
of  the  clear  span,  or  at  the  quarter  point  of  the  center  to  center 
spacing  of  the  columns,  using  the  higher  value  in  every  case.  The 
point  of  bend  in  the  bent  bars,  and  also  the  length  of  the  extra 
short  rods  in  the  top,  will  be  governed  by  this  dimension. 

In  the  end  panels  the  area  of  the  reinforcement  perpendicular 
to  the  wall  should  be  increased  by  the  usual  20  per  cent.     The 


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242   Trelease  on  Design  of  Concrete  Flat  Slabs. 


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FIQ.  22. — ^MOMENTS  PER  UNIT  WIDTH  USED  IN  DESIGN. 


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Trelease  on  Design  op  Concrete  Flat  Slabs.       243 

easiest  way  to  do  this  is  to  use  round  bars  in  the  interior  panels, 
and  square  bars  of  the  same  nominal  size  and  spacing  in  the  end 
panels.  In  order  to  facilitate  the  placing  of  the  reinforcement,  it 
will  be  found  necessary  to  provide  light  bars,  preferably  |  in. 
round,  along  the  sides  of  the  panels,  so  that  they  may  be  used  to 
support  the  bent  bars.  Of  course,  these  spacing  bars  may  be 
figured  as  effective  in  tension  over  the  top  of  the  colunm,  and  thus 
replace  some  of  the  short  bars  used  there. 

Table  II  gives  recommended  dimensions  for  flat  slab  floors 
to  suit  various  live  loads  and  panel  sizes.  The  table  is  based  on 
a  maximimi  theoretical  concrete  stress  of  750  lb.  per  sq.  in.  The 
slab  thicknesses  are  such  that  the  deflections  under  a  superimposed 
test  load  equal  to  once  the  dead  load  plus  twice  the  live  load 
will  not  exceed  one  five-hundredth  of  the  span  for  a  theoretical 
working  stress  in  the  reinforcement  of  18,000  lb.  per  sq.  in.  Ten- 
sion in  the  concrete,  arch  action,  etc.,  all  tend  to  reduce  the  actual 
stresses  below  the  theoretical  values,  but  no  building  code  will 
permit  these  factors  to  enter  into  the  design  of  concrete  structures. 

Flat  slab  designs  showing  smaller  column  head  diameters, 
or  thinner  slabs  over  the  supports,  than  those  given  in  the  table 
should  be  carefully  checked  for  shear  at  the  edge  of  the  column 
heads. 

To  illustrate  the  application  of  this  new  method  for  the 
computation  of  flat  slabs,  the  detailed  design  of  a  typical  panel 
will  be  given.  To  enable  comparison  of  the  results  with  those 
obtained  by  other  methods  described  and  tabulated  by  Mr.  Angus 
B.  McMillan  in  a  paper*  before  the  Association,  a  panel  20  ft. 
square  will  be  designed  for  a  live  load  of  200  lb.  per  sq.  ft.,  using  a 
steel  stress  of  16,000  lb.  per  sq.  in.  and  a  ratio  of  the  moduli  of 
steel  and  concrete  of  15. 

In  Table  II  under  the  above  span  and  loading  a  slab  thickness 
of  8  in.  is  given,  with  a  2  in.  cap  8  ft.  square,  and  a  column  head 
50  in.  in  diameter.  The  average  weight  of  the  slab,  including  the 
cap,  is  104  lb.  per  sq.  ft. 

The  clear  span  from  edge  to  edge  of  colimMi  heads  is  15.83  ft., 
and  the  "gross  bending  moment"  or  wS^  is  12X304X15.83^  or 
914,150  in.-lb.  per  ft.  of  width.      Referring  to  Fig.  22,  it  will  be 


*  Proeudingg,  Vol.  VI,  p.  248.— Ed. 


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244       Trelease  on  Design  op  Concrete  Flat  Slabs. 


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Trblease  on  Design  op  Concrete  Flat  Slabs.       245 

seen  that  the  net  positive  moment  for  the  central  strip  of  the  slab 
is  1/40  of  the  gross  moment,  or  22,850  in.-lb.  per  ft. 

To  enable  the  comparison  with  Mr.  McMillan's  table,  the 
efifective  depth  of  the  slab  will  be  taken  as  7  in.,  so  that  the  area 
of  reinforcement  per  foot  width  of  this  strip — 

^«=  - — J?^-^^,  or  0.237  sq.  in. 
7 X. 86  X  16,000'  ^ 

This  will  be  supplied  by  using  |-in.  corrugated  round  bars 
spaced  15  in.  on  centers.  The  negative  moment  for  this  strip  is 
of  the  same  magnitude  as  the  positive,  so  that  it  can  be  properly 
taken  care  of  by  bending  up  every  other  bar  in  this  strip  and  in 
the  corresponding  strips  of  the  adjacent  panels. 

At  the  center  of  the  next  strip,  there  is  a  positive  moment 
equal  to  1/30  of  the  gross  moment,  or  30,470  in.-lb.,  requiring  an 
area  of  reinforcement  per  foot — ^il3o  =  0.316  or  f-in.  roimds,  11 J  in. 
on  centers. 

Over  the  edge  of  the  panel  the  negative  moment  for  this 
strip  is  1/15  of  the  gross  moment,  or  60,940  in.-lb. — 

An^ ^^^^  or  0.492  sq.  in.  p3r  ft. 

9X.86X  16,000'  ^         ^ 

If  every  other  bar  from  the  bottom  of  thi?,  band  is  bent  up, 
there  are  0.316  sq.  in.  per  ft.  and  the  rema'nder,  0.172,  can  be 
supplied  in  the  form  of  short,  straight  bars,  using  f-in.  rounds 
spaced  21  in.  on  centers. 

For  the  strip  or  band  at  the  edge  of  the  panel  the  net  positive 
moment  is  1/20  of  the  gross  moment,  or  45,710  in.-lb.,  calling  for 
ilM  =  0.474  sq.  in.  per  ft.,  or  f-in.  rounds  spaced  7.5  in.  on  centers. 
At  the  ends  of  this  strip  over  the  column  head  the  net  negative 
moment  is  1/10  of  the  gross  moment,  or  91,415  in.-lb.,  requiring 
-4io  =  0.738  sq.  in.  per  ft.  The  bent  bars  will  supply  0.474  sq. 
in.  per  ft.,  so  that  the  remaining  0.264  sq.  in.  will  be  taken  care  of 
by  short  straight  bars,  using  f  in.  rounds  spaced  13.5  in.  on  centers. 

The  length  of  the  short  straight  bars  will  be  such  that  they 
will  reach  the  fifth  point  of  the  clear  span,  so  that  they  will  be 
10  ft.  6  in.  long  for  this  panel. 

Having  determined  the  size  and  spacing  of  the  bars  they  can 
be  laid  out  on  a  drawing,  or  the  number  required  estimated  in 
the  following  manner: 


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246       Trelease  on  Design  of  Concrete  Flat  Slabs. 

The  balanced  average  of  the  moment  factors  in  Fig.  22  for  the 
positive  moments  at  the  center  of  the  panel  is  30,  so  the  net  moment 
is  30,470  m.-lb.  per  ft.,  or  m  the  20  ft.  width  of  panel,  609,400 
in-lb.  To  resist  this  moment  will  require  6.33  sq.  in.  of  reinforce- 
ment, or  twenty-one  f  in.  romid  bars.  The  average  area  of  the 
short  top  bars  required  is  0.218  sq.  in.  per  ft.,  and  the  total  width 
in  which  they  must  be  supplied  is  10  ft.,  so  that  2.18  sq.  in.,  or  say 
seven  f-in.  round  bars  are  required. 

This  gives  the  total  number  of  bars  in  one  direction;  in  the 
whole  panel  there  are  21  straight  bars  21  ft.  long,  21  bent  bars 
31  ft.  long,  and  14  straight  bars  10  ft.  6  in.  long,  all  f-in.  round,  or  a 
total  of  1300  lb.  of  reinforcement  per  panel.     Table  III  gives  a 


Table  III. — Quantity  of  Reinforcement  Required  Per  Panel  Under 

Various  Designs  with  a  Unit  Reinforcement  Stress  of 

16,000  Lb.  per  Sq.  In. 


Method. 

Thickneae 
of  Slab,  in. 

Pounds  of 
Reinforcement. 

Ca&tQeyar 

8 

12 
8 
8 
8 
8 

V 

2,189 

TiimfMiira and  Mauror. 

i;931 

Grashof 

784 

Mensch 

2,120 

Turner. 

649 

McMillan 

1,084 

Brayton. 

1.900 

TrelmlM) r   r   .    .   r    r 

1,300 

comparison  of  the  quantity  of  reinforcement  required  under  various 
designs. 

Fig.  23  shows  the  arrangement  of  the  reinforcement  in  this 
t3^ical  panel.  To  avoid  confusion  in  the  drawing,  the  bars  from 
the  adjoining  panels  are  not  shown.  In  designing  this  slab,  it 
has  been  assumed  that  the  slab  is  fixed  at  the  edge  of  the  column 
head,  as  it  is  the  general  practice  to  flare  the  head  at  a  small  angle, 
making  it  very  rigid.  The  head  is  not  counted  on  to  resist  bending 
moment,  and  is  flared  merely  to  take  care  of  the  shear  and  to 
somewhat  reduce  the  clear  span. 

To  compute  the  deflection  of  the  typical  panel  designed,  the 
deflection  of  a  strip  of  unit  width  at  the  side  of  the  panel  will  be 
computed  and  also  of  a  unit  strip  at  the  middle  of  the  panel,  and 
the  total  deflection  of  the  plate  taken  as  the  sum  of  these.    It  will 


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Treleasb  on  Design  op  Concrete  Flat  Slabs.       247 

first  be  assumed  that  these  strips  are  freely  supported,  and  the 
deflections  transformed  later  by  the  ratio  of  the  deflection  coeflS- 
cients  given  in  Fig.  12  to  those  for  simply  supported  beams.    The 


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FIQ.  23. — ARRANGEMENT  OF  REINFORCEMENT  IN  TTPICAL  PANEL. 

computations  may  be  very  quickly  made  by  using  the  graphical 
solution  of  Mr.  White's  method  published  in  Dodgers  Diagrams. 
In  this  way  the  deflection  at  the  working  reinforcement 


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248      Trelease  on  Design  op  Concrete  Flat  Slabs. 

stress  of  16,000  lb.  per  sq.  in.  is  found  to  be  0.15  in.,  or  1/1600  of 
the  panel  side.  For  higher  stresses  the  deflection  would,  of  course, 
be  greater. 

The  unit  stresses  which  have  been  employed  for  this  panel 
are  very  conservative,  and  could  be  safely  increased  to  18,000  lb. 
on  the  reinforcement  and  750  lb.  on  the  concrete.  In  this  particu- 
lar panel  the  maximum  concrete  stress  is  at  the  colunm  head  and 
is  only  600  lb.  per  sq.  in.,  while  at  the  center  of  the  side  band 
eth  concrete  stress  is  about  550  lb.  With  the  50-in.  column  head 
used  the  shear  over  jd  is  about  100  lb.  per  sq.  in.  and  as  this  is 


MG.   24. — TEST  LOAD   ON  PANEL  IN  ST.   LOUIS. 

pimching  shear,  such  as  in  footings,  a  higher  value  could  be  used 
if  desired. 

Floors  designed  in  accordance  with  the  methods  outlined  in 
this  paper  have  been  built  in  several  cities,  and  a  few  have  been 
thoroughly  tested.  In  these  tests,  both  reinforcement  and  concrete 
stresses  have  been  measured  by  extensometers.  The  floors  tested 
were  designed  for  reinforcement  stresses  of  20,000  lb.  per  sq.  in. 
with  the  exception  of  the  building  in  Minneapolis,  where  18,000 
lb.  was  used.  These  theoretical  stresses  were,  of  course,  not 
realized  in  the  tests  as  tension  in  the  concrete,  arch  action,  etc., 
were  not  taken  into  account  in  the  designs. 

Fig.  24  shows  a  panel  in  a  factory  in  St.  Louis  under  a  test 


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Trelease  on  Design  op  Concrete  Flat  Slabs.       249 

load  of  400  lb.  per  sq.  ft.  The  panel  was  20  ft.  i  in.  by  22  ft., 
designed  for  a  safe  live  load  of  150  lb.,  with  an  8-in.  slab.  The  slab 
was  inverted  in  this  case,  giving  a  perfectly  flat  ceiling.  Two  inch 
caps  were  to  be  cast  on  the  top  and  hidden  in  the  cinder  fill,  and 
the  drawings  showed  the  bars  bent  up  into  them.  As  actually 
constructed,  the  reinforcement  in  this  panel  had  an  effective 
depth  over  the  column,  the  critical  point  of  the  structure,  of  but 
60  per  cent  of  that  shown  on  the  drawings.     Even  under  these 


FIG.  25. — ADDITION  TO  THE  FORD  MOTOR  COMPANY'S  FACTORY,  DETROIT,  MICH. 

adverse  conditions,  the  maximmn  reinforcement  stress  over  the 
column  head  under  the  full  test  load  was  but  17,000  lb.,  and  the 
concrete  stress  at  this  point  950  lb.  The  reduction  of  the  effective 
depth  over  the  column  caused  a  large  reduction  of  the  moment  of 
inertia  at  that  point,  giving  conditions  approaching  those  in  a 
freely  supported  panel,  as  the  stresses  and  deflections  clearly 
indicate.  The  deflection  increased  from  the  normal  amount  for  a 
fixed  panel  to  0.68  in.  imder  full  test  load,  somewhat  less  than  the 
normal  amount  for  a  free  span.    The  average  reinforcement  stress 


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250      Trelease  on  Design  of  Concrete  Flat  Slabs. 

at  the  middle  of  the  panel  was  also  increased  in  like  manner  to 
25,000  lb.  per  sq.  in. 

Perhaps  the  most  severe  test  of  a  floor  was  one  made  in 
Minneapolis  in  which  four  panels  of  a  warehouse  floor  were  loaded.  * 
The  building  as  laid  out  was  not  well  adapted  to  flat  slab  floor 
construction,  because  of  the  number  and  shape  of  the  panels. 
There  was  one  row  of  colunms  through  the  building,  dividing  the 
floor  into  panels  13  ft.  6  in.  by  19  ft.  11  in.;  with  the  short  side 
resting  on  brick  bearing  walls.  An  8-in.  slab  was  used  for  the 
200  lb.  live  load  required.  Four  panels  of  the  floor  were  loaded 
with  cement  piled  to  prevent  arching,  and  very  complete  readings 
of  stresses  and  deflections  were  made.  Under  the  maximum 
superimposed  load  of  400  lb.  per  sq.  ft.  the  deflection  at  the  middle 
of  the  panels  averaged  0.39  in.,  a  very  good  figure  remembering 
that  the  panels  were  free  at  one  end.  The  reinforcement  stress 
over  the  column  head  was  23,000  lb.,  and  at  the  mid-point  of  the 
span  13,500  lb.  The  concrete  stress  had  a  maximum  value  at 
the  column  head  of  1050  lb.  per  sq.  in.  These  stresses  show  the 
design  to  be  conservative. 

Fig;  25  is  a  view  of  a  factory  in  Detroit  having  floors  and 
roof  of  this  type  of  flat  slab.  The  panels  are  25  x  20  ft.  and  the 
floors  were  designed  for  150  lb.  per  sq.  ft.,  using  an  8-in.  slab, 
2-in.  cap  and  48-in.  colunm  head.  One  panel  of  the  floor  was 
loaded  with  gravel  to  300  lb.  per  aq.  ft.  Under  this  load,  the 
deflection  was  found  to  be  0.60  in.  The  reinforcement  stress 
over  the  column  head  was  13,500  lb.  per  sq.  in.  and  at  the  center 
of  the  slab  13,850  lb.,  showing  a  well-balanced  design. 

These  tests  seem  to  show  quite  conclusively  that  the  method 
of  design  outlined  can  be  used  for  almost  any  condition  of  span 
and  loading  with  confidence  as  to  the  resulting  strength  of  the 
structure. 


*  For  complete  data  of  test  see  Report  of  Committee  on  Reinforoed  Conorete  and  Buildiag 
Laws.  p.  IOS.—Ed. 


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DISCUSSION. 


Mr.  Alfred  E.  Lindau. — ^The  object  of  the  test  was  to  gain  Mr.  Lindaa. 
some  knowledge  of  the  action  of  an  elastic  slab,  supported  on 
points,  under  a  uniform  load.  At  the  time  the  tests  were  under- 
taken it  was  not  expected  to  obtain  a  great  deal  of  information 
that  could  be  used  in  actual  designing  of  concrete  structures,  but 
rather  some  idea  of  the  nature  of  the  deformations;  by  plotting 
the  deformations  obtain  the  deflection  of  the  surface  and  perhaps 
determine  points  of  inflection,  rate  of  change  of  curvature  at  the 
various  points  and  perhaps  some  idea  of  the  relative  deformation 
for  various  points  of  the  slab. 

Many  suggestions  were  made  as  to  the  material  to  be  used 
in  making  this  preliminary  investigation.  It  was  suggested  that 
a  steel  plate  be  polished  and  by  some  mirror  apparatus  obtain 
those  deformations.  Hard  rubber  was  also  suggested,  plaster 
plates  were  tried  as  well  as  a  cement  coated  wire  screen — ^all  of 
which  gave  some  valuable  information  but  did  not  give  the 
information  desired  and  the  results  would  not  have  been  of  any 
particular  interest. 

Mr.  Arthur  N.  Talbot. — ^I  have  been  very  much  interested  Mr.  T«iboc 
in  the  experiments  made  by  Mr.  Trelease.  They  show  the  dis- 
tribution of  bending  moment  in  a  homogeneous  slab  of  rubber  in 
a  way  which  could  not  be  obtained  by  mere  computation.  The 
negative  moments  at  and  between  the  supports,  the  relative 
values  of  the  positive  bending  moments  at  the  center  of  the 
panels  are  well  brought  out  and  there  are  many  features  of  the 
results  which  will  be  helpful  in  the  application  to  design  problems. 
Of  course,  we  have  here  a  material  that  resists  tension  all  through 
it,  as  well  as  compression  and  one  having  a  modulus  of  elasticity 
much  the  same  in  tension  as  in  compression.  In  the  case  of 
ordinary  flat  slab  construction  the  concrete  is  in  compression  on 
one  side  and  has  a  reinforcement  of  steel  on  the  other  to  take 
most  of  the  tensile  stresses.  The  conditions  in  the  test  must  be 
kept  in  mind  because  they  are  different  from  those  of  reinforced 
concrete.     Rubber  is  a  material  with  a  very  low  modulus  of 

(251) 


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262  Discussion  on  Concrete  Flat  Slabs. 

Mr.T«ibot  elasticity,  a  material  that  even  under  small  deflections  would 
bring  in  the  question  of  catenary  action,  rather  more  than  beam 
or  slab  resistance. 

I  wish  to  ask  whether  in  the  experiments  an  eflfort  was  made 
to  determine  the  eflfect  on  the  elasticity  or  on  the  deformations 
occurring  when  the  rubber  was  stretched  or  compressed  in  two 
directions.     This  has  a  bearing  on  slab  action. 

Mr.  Lindaa.  Mr.  Lindau. — There  was  an  attempt  made  to  obtain  such 

results,  but  some  difficulty  was  encountered  in  getting  satisfac- 
tory compression  tests  on  the  strips  used.  The  results  on  the 
lateral  deformation  in  tension  were  quite  satisfactory  and  seemed 
to  give  very  uniform  results,  but  the  compressive  test  did  not 
show  up  quite  so  well.  The  rubber  was  only  stretched  in  one 
direction.  The  question  of  obtaining  lateral  deformation  was 
discussed  at  considerable  length  but  tests  were  not  carried  out, 
largely  on  account  of  lack  of  time. 

Mr.  Talbot.  Mr.  Talbot. — The  matter  of  compressive  strength  is  one  of 

considerable  importance  in  flat  slab  construction,  for  with  a 
rather  small  percentage  of  reinforcement  in  each  of  four  direc- 
tions, or  even  two  directions,  the  combined  calculated  stress  may 
nm  high,  unless  reinforcement  in  compression  is  used,  which  to 
my  mind  is  not  a  very  satisfactory  arrangement  with  this  type  of 
construction.  It  may  be  expected  that  when  concrete  is  sub- 
jected to  compressive  stresses  in  two  directions,  its  resisting 
strength  will  not  be  the  same  as  when  the  pressure  is  applied  in 
only  one  direction.  It  is  true — ^and  this  has  a  bearing  upon  the 
distribution  of  stresses  between  the  reinforcement  and  concrete 
in  such  construction — that  the  amoimt  of  compressive  deforma- 
tion resulting  from  applying  a  given  load  is  less  when  the  load  is 
applied  in  two  directions  than  when  it  is  applied  in  one;  that 
seems  to  be  the  result  of  some  experiments  which  we  have  made 
and  which  agree  with  tests  made  elsewhere.  Specimens  were 
made  up  in  the  form  of  a  cross  and  a  load  applied  in  one  direction 
and  also  in  two  directions  and  measurements  taken  on  the  con- 
crete in  the  cross  portion  and  in  the  arms  of  the  cross;  and, 
making  a  comparison,  there  seems  to  be  less  shortening  in  the 
concrete  where  it  is  stressed  in  two  directions,  and  of  course  a 
greater  expansion  in  the  direction  at  right  angles  than  when  the 
compressive  stress  is  applied  in  only  one  direction. 


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Discussion  on  Concrete  Flat  Slabs.  253 

We  have  attempted  to  make  tests  of  cubes  by  appljdng  com-  ^r.  T«ibot. 
pression  against  four  faces  instead  of  two.  The  first  tests  showed 
considerably  greater  strength  for  loads  applied  in  two  directions 
than  in  one,  but  we  felt  that  a  large  part  of  this  difference  was  due 
to  the  restraint  of  the  loading  faces  themselves,  the  friction  along 
the  face,  which  kept  the  concrete  from  expanding  laterally.  We 
then  made  other  tests  by  lubricating  the  faces  of  the  bearing 
blocks  very  carefully  and  the  values  for  compression  in  two 
directions  were  approximately  the  same  as  those  in  one. 

I  may  add  that  measurements  were  made  on  cantilever  slabs, 
slabs  composed  of  what  you  may  think  of  as  the  column  capital 
and  the  part  of  the  floor  slab  out  to  the  line  of  inflection,  support- 
ing them  at  this  line  of  inflection,  just  as  the  load  of  the  remain- 
der of  the  panel  would  be  suspended  in  an  analysis  of  the  flat 
slab — omitting,  you  will  see,  the  uniform  load  for  the  central 
portion  immediately  surrounding  the  column — ^measurements  of 
the  deformations  of  the  reinforcement  were  made.  We  find  that 
in  the  middle  line  of  the  band  the  maximum  stress  is  the  greatest 
at  the  edge  of  the  column  capital;  that  the  stress  decreases  pretty 
regularly  from  there  to  the  edge  of  this  cantilever  slab,  the  line 
of  inflection;  that  through  the  middle  portion  immediately  over 
the  column  capital  it  decreases  rapidly,  although  it  does  not 
become  zero  with  the  ordinary  size  of  bars  even  directly  over  the 
center  of  the  column;  that  along  the  edges  of  the  bands  the 
maximum  stress  in  the  rods  is  somewhat  further  in,  nearer  the 
center  of  the  length  of  the  reinforcing  bars.  The  maximum 
stress  in  the  bar  at  the  middle  of  the  band  does  not  differ  far  from 
the  maximum  stress  in  the  bar  at  the  edge  of  the  band,  even 
though  its  position  differs  considerably. 


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THE  PRACTICAL 
DESIGN    OF    REINFORCED    CONCRETE    FLAT   SLABS. 

By  Sanford  E.  Thompson.* 

The  purpose  of  this  paper  is  to  present  material  covering 
the  practical  task  of  designing  flat  slab  floors  for  reinforced  con- 
crete structures.  The  requisite  thickness  of  slab,  amount  of 
reinforcement  and  size  of  column  head  for  different  loadings  and 
different  spans  are  given  in  Tables  I-IV;  and  the  theories  and 
assumptions  involved  in  the  computation  are  briefly  discussed. 
Values  not  included  in  the  tables  may  be  worked  out  from  the 
formula,  finding  the  desired  values  of  C^  and  C,  from  the  dia- 
grams.! Curves  are  given  also  for  the  constants  used  in  the 
design  of  members  with  reinforcement  in  top  and  bottom,  and 
apply  not  only  to  flat  slabs,  but  to  any  beam  or  slab  reinforced 
both  in  compression  and  tension. 

For  reinforced  concrete  buildings,  the  flat  slab,  or  girderless 
floor, — ^as  it  is  sometimes  called, — ^is  as  cheap,  and  frequently 
cheaper,  than  beam  and  girder  construction.  The  smooth  ceil- 
ings with  no  intersecting  beams  allow  better  distribution  of  the 
light.  The  expense  and  complication  of  installing  sprinkler 
systems  are  reduced.  The  clear  headroom  for  the  same  story 
height  is  increased,  or  else,  on  the  other  hand,  the  story  height 
may  be  made  less  without  reducing  the  effective  headroom.  This 
last  consideration  alone  is  often  important  enough  to  dictate  flat 
slab  floors. 

With  flat  slab  floors  the  entire  load  is  supported  directly  on 
the  columns,  which  are  usually  spaced  about  equally  in  both 
directions.  The  column  heads  are  enlarged  so  as  to  give  increased 
resistance  in  shear  and  bending  at  the  points  where  this  is  most 
needed.  The  reinforcing  bars  run  through  the  slabs  over  the 
colunm  heads  in  four  directions,  two  rectangular  and  two  diagonal. 

The  simplest  way  of  considering  the  flat  slab  is  to  assmne 

*  Consulting  Engineer,  Newton  Highlands,  Mass. 

t  For  an  example  of  flat  slab  design  worked  out  in  detail  see  Taylor  and  Thompson's 
''Concrete,  Plain  and  Reinforced."  2d  edition,  1011.  pages  487  and  488. 

(254) 

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Thompson  on  Design  of  Concrete  Flat  Slabs.      255 

that  a  portion  of  the  slab  extending  a  certain  distance  out  from 
the  column  is  a  flat,  circular  plate,  similar  to  a  Japanese  parasol, 
but  with  no  slope  to  its  surface.  This  plate  is  fixed  to  the  colunm 
and  is  assumed  to  extend  out  from  it  on  all  sides  like  a  canti- 
lever as  far  as  the  line  of  inflection  of  the  slab,  which  line, — as 
in  other  forms  of  monolithic  construction, — ^is  about  one-fifth  of* 
the  net  span  away  from  the  support.  The  rest  of  the  slab  may  be 
considered  as  entirely  separate  from  the  flat  circular  plates  but 
simply  supported  from  their  outer  edges  or  circumferences. 

This  is  no  new  theory  but  is  somewhat  similar  in  effect  to 
that  of  a  imiformly  loaded,  fixed  or  continuous  beam.  To  illustrate 
this  in  practical  fashion,  an  ordinary  beam  uniformly  loaded 
and  fixed  at  both  ends  will  be  considered.  This  illustration  does 
not  in  any  way  show  the  methods  of  determining  a  bending 
moment  in  the  flat  slab,  since,  as  stated  below,  the  actual  bending 
moment  is  dependent  upon  the  elastic  tjieory.  It  does,  however, 
show  quite  clearly  the  justification  of  assuming  the  slab  to  be  cut 
through  on  the  line  of  inflection. 

It  is  known  from  simple  mechanics  that  the  moment  at  the 
support  of  an  ordinary  fixed  or  uniformly  loaded  continuous  beam 
is  Wl/12*  and,  at  the  center,  is  TFZ/24.  Now,  suppose  at  the 
points  of  inflection,  which  also  by  mechanics  are  known  to  be 
located  at  a  distance  0.21 13Z  from  each  support,  the  beam  is  cut 
completely  through  so  as  to  have  a  cantilever  at  each  end  with 
a  simply  supported  beam  between.  The  bending  moment  of 
the  cantilever  at  its  support,  due  to  the  load  upon  it,  is  0.2113 
TrX0.2113Z/2,  and  the  moment  at  its  support  due  to  the  load  on 
the  supported  beam  between  cantilevers,  is  [1—2  (0.2113)]2 
WX0.2n3l.  The  sum  of  these  two  moments  is  0.0223 
m+0.0610  FZ= 0.0833  Wl  or  Wl/12.  In  other  words,  while 
this  analysis  is  not  that  which  can  be  used  for  a  flat  slab,  because 
of  the  extra  strength  of  the  flat  slab  due  to  the  multiple  reinforce- 
ment, the  division  into  sections  corresponds  to  our  assumption 
in  the  flat  slab  theory.  In  the  same  way  it  might  be  shown  that 
the  center  moment  of  the  simple  beam  supported  by  the  two 
ordinary  cantilever  beams  is  Wl/24. 

Tests  of  the  flat  slab  construction  at  Minneapolisf  indicate 

*  W  *■  total  live  plus  dead  load.    I  >"  distance  in  feet  between  supports. 
t  See  paper  on  "A  Test  of  a  Flat  Slab  Floor  in  a  Reinforced  Concrete  Building, "  by  Arthur 
R.  Lord,  ProeeeditHf,  VoL  VII.  page  166. 


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256      Thompson  on  Design  of  Conckbtb  Flat  Slabs. 

that  the  line  of  inflection  of  a  flat  slab  floor  is  substantially  the 
same  as  in  a  fixed  beam,  or  about  ^/s  the  net  distance  between  sup- 
ports, although,  as  would  be  expected,  the  bending  moment  is 
entirely  diflferent. 

Problem  of  Design. 

The  problem  of  the  design  of  the  flat  slab,  then,  resolves  it- 
self into  (1)  a  determination  of  the  proper  thickness  and  reinforce- 
ment required  at  the  support  for  the  cantilever  circular  plate 
supporting  its  own  load  and  also  the  load  of  the  rest  of  the  slab, 
and  (2)  a  determination  of  the  thickness  and  reinforcement  at  the 
center  of  the  span  required  for  the  simply  supported  section  lying 
between  the  circular  plates. 

Various  Methods  of  Design  of  Slab. 

Various  methods  have  been  advanced  for  the  design  of  the 
flat  slab.  Some  are  based  merely  on  deflection  tests,  which  give  no 
true  basis  for  computations;  others  compute  the  reinforcement 
carefully  at  the  center  of  the  slab,  which  is  not  the  critical  part; 
others  consider  the  construction  to  consist  of  beams  between 
columns  with  a  slab  between,  thus  obtaining  ultra-conservative 
results;  while  a  plan  still  more  common  is  to  take  the  moment 
at  the  supports  arbitrarily  without  regard  to  the  size  of  the  col- 
umn head.  The  shear  or  diagonal  tension  near  the  column  head 
is  frequently  disregarded  altogether. 

Shear  at  the  Support. 

The  direct  shear  at  the  support,  as  in  any  mechanical  con- 
struction, is  equivalent  to  the  total  load  supported  by  the  column. 
This  shear  is  readily  borne  by  the  concrete  and  reinforcement. 
The  diagonal  tension,  however,  which,  as  in  a  beam,  may  be 
considered  as  measured  by  direct  shear,  must  be  carefully  con- 
sidered. To  reduce  the  diagonal  tension  and  also  to  increase 
the  resistance  to  bending  of  the  slab,  the  column  head  is  enlarged. 
To  still  further  increase  the  resistance,  a  part  of  the  bars  in  the 
top  of  the  slab  over  the  supports  may  be  bent  down  just  outside 
of  the  supports  and  then  carried  along  in  the  bottom  of  the  slab. 

In  either  case,  the  shearing  stress  should  be  limited  to  definite 


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Thompson  on  Design  op  Concrete  Flat  Slabs.       267 

units,  although  it  seems  permissible  to  use  a  somewhat  higher 
stress  than  in  a  beam. 

The  diameter  of  the  enlarged  column  head,  which  is  the  actual 
support  of  the  slab,  should  be  governed  by  the  shearing  stress 
either  at  its  circumference  or  at  a  short  distance  outside  of  it. 

Bending  Moment  at  Support. 

The  theory  of  flat  plates,  which  must  be  used  in  designing  a 
circular  plate,  is  not  yet  clearly  established.    By  the  use  of  what 


rr-rXL        M    Ada'^med  iine  of        I  f/ 

II     'n* — 'f^iAy  mctxJmum  bending    i  (( 

\\        \\  /  7       .'  /  moment  .  \ 

t  r^- — ^  ^f  ^Theoretical  t!ne  \ 

\\       Column  head^/y     of  inflection       \ 
\   >v     .  /  /       ^Assumed  iine      v 

^^>-r-j— jy<-^^     ^  of  inflection  ^^_ 

FIG.    1. — PLAN   OF  FLAT  SLAB. 

is  termed,  in  mechanics,  the  elastic  theory,  we  have  a  fairly  good 
working  hypothesis.  The  analysis  solved  by  Prof.  H.  T.  Eddy* 
offers,  in  the  writer's  judgment,  the  most  rational  solution  of  the 
problem  yet  advanced. 

In  the  design  of  the  flat  slab,  therefore,  the  authorf  has  started 
with  Prof.  Eddy's  analysis  of  stresses  in  a  homogeneous  circular 
plate,  and  from  his  general  formulas  has  deduced  by  mathematics 

*  EDgineers'  Society,  University  of  Michigan,  1899. 

t  The  author  i«  indebted  to  Mr.  Edward  Smuloki  for  the  oomputationB  involving  intricate 
analyses  by  higher  mathematics;  also  to  Mr.  John  Ayer  for  further  studies  in  the  practical 
design. 


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258      Thompson  on  Design  of  CoNCRfiTfi  Flat  Sla^s. 

other  formulas  applying  to  circular  plates  free  on  their  edges  and 
clamped  around  the  columns.  In  a  flat  slab  thus  supported  there 
are  horizontal  stresses  at  right  angles  to  each  other.  The  eflfect  of 
these  lateral  stresses  has  been  taken  into  account,  this  being  ex- 
pressed by  Poisson's  ratio,  which  is  the  ratio  of  the  lateral  deforma- 
tion to  the  deformation  in  the  direction  of  the  stress.  The  value 
of  this  ratio  is  taken  as  0.1,  which  has  been  shown  by  experiments 
to  be  a  fair  value  for  concrete  of  1  :  2  :  4  proportions. 

It  has  been  found  possible  to  reduce  the  complicated  formulas 
derived  by  the  Eddy  analysis  into  four  formulas  which  are  com- 
paratively simple  although  still  rather  complicated  for  practical 
use.     These  formulas  are  for  four  bending  moments  and  can  be 


2t 


u^ 


1%0  In  pouftds  ptraifuare  foot 
1  1  1  I  1  1  iiiiiil  li  i  1  11 


il 


^Isi^ 


r$etangular  itett  in 
two  tayera 


q  In  pounds  par  linear  foot 

no.  2. — 8EcnoN  of  flat  slab. 


applied  not  merely  to  the  slab  at  the  support,  but  to  any  point  in 
the  circular  plate  surrounding  the  column.  The  four  moments 
are  as  follows: 

Ml  =  moment  produced  by  the  loading  that  is  uniformly  distrib- 
uted over  the  circular  plate  and  causes  circumferential 
fibre  stress. 

Jlf  2— moment  produced  by  this  same  loading  but  which  causes 
radial  fibre  stress. . 

Mo = moment  produced  by  the  loading  from  the  rest  of  the  slab 
that  is  distributed  along  the  outer  edge  of  plate  and 
causes  circumferential  fibre  stress. 

Mb « moment  produced  by  the  latter  loading  but  which  causes 
radial  fibre  stress. 


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Thompson  on  Design  of  Concrete  Flat  Slabs.       259 

A  study  of  the  analysis,  however,  shows  that  the  two  cir- 
cumferential moments  are  a  minimum  at  the  support  and  may  be 
safely  disregarded.  The  two  formulas  for  the  radial  moment  may 
be  combined  and  still  further  reduced  to  the  following  simple 
form  which  can  be  used  for  a  circle  of  any  radius,  r,  within  the 
circular  plate.  The  meaning  of  the  symbols  is  made  clearer  by 
reference  to  Figs.  1  and  2,  which  show  the  plan  and  the  section 
of  a  flat  slab. 

Let 
q    =    uniformly  distributed  load  around  the  outer  edge  of  the 

plate  in  lb.  per  ft.  of  length. 
w    «    uniformly  distributed  load  on  surface  of  plate  (including 

dead  load)  in  lb.  per  sq.  ft. 
r«    =    radius  in  feet  to  line  of  maximum  bending  moment  (which 

is  within  the  column  head). 
fi    =    outer  radius  of  assumed  plate  in  feet, 
r    =    any  radius  in  feet  where  moment  is  to  be  computed;  for 

critical  section,  r  is  radius  of  column  head. 
Ci,  Ce  =  constants  given  in  Figs.  3  and  4. 
Mr  s  total  radial  bending  moment  to  be  used  ordinarily. 
h    »    distance  in  feet  between  lines  of  inflection. 

Then  total  radial  moment  at  any  point  of  plate  is 
Mr=wrlCi  +  qr^^ 

For  convenience  in  computation,  values  of  the  constants 

T  T 

C5  and  C„  for  various  values  of  the  ratios  -^  and  -  are  plotted 

in  the  curves  given  in  Figs.  3  and  4.* 

With  q  expressed  in  lb.  per  ft.  of  length,  w  in  lb.  per  sq.  ft., 
and  To  in  ft.,  the  moments  are  in  ft.-lb.  per  ft.  or  in.-lb.  per  in. 

Position  op  Maximum  Bending  Moment  and  op 
Maximum  Stress. 

As  commonly  constructed,  the  column  head  flares  at  the 
top  and  is  therefore  more  or  less  flexible.  For  this  reason  the 
line  of  maximum  bending  moment  will  be  located,  not  at  the 

*  TheM  Are  drawn  up  from  values  in  tables  in  Taylor  and  Thompson's  **  Concrete,  Plain 
•Bd  Rsiaforoed."  Sd  edition.  1911,  pate  618. 


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260      Thompson  on  Design  op  Concrete  Flat  Slabs. 


1.0        1.1        La       13       M-       1.5       1.6       1.7        18      L9       2X) 
Values  of£ 

FIQ.    3. — ^DIAGRAM    GIVING   VALUES   OW   Cf  IN   VORMULA 

Mr-  w  To*  C^  +  qr^  C$ 
foi- radius  in  feet  to  line  of  maximum  bending  moment. 
n  « outer  radius  of  assumed  plate  in_feet. 

r—any  radius  in  feet  where  moment  ia  to  be  computed  for  actual  aeotkni 
ordinarily  r  is  radius  of  column  head. 


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Thompson  on  Design  op  Concrete  Flat  Slabs.      261 


1.0       If    .    L2,       13       lA      L5       I.B      IT       L8      1.3       iO 
Valuer  of-| 

FIG.   4. — DLIGRAII   GIVING   VALUES   OF   Cg   IN   FORMULA 
Mr^W  To*  Ct  +  q  fo  C# 

r«"  radius  in  feet  to  line  of  maximum  bending  moment. 

n  » outer  radius  of  assumed  plate  in  feet. 

r""any  radius  in  feet  where  moment  is  to  be  computed  for  actual  section , 

ordinarily  r  is  radius  of  column  head.  ^^  j 

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262      Thompson  on  Design  of  Concrete  Flat  Slabs. 

extreme  edge  of  the  column  head,  but  a  little  within  it.  The 
maximum  stress,  on  the  other  hand,  will  not  be  on  the  line  of 
the  maximum  bending  moment  because  the  strength  there  (since 
it  is  within  the  head)  is  increased  due  to  the  greater  depth  of 
concrete.  It  is  fair  to  assume,  therefore,  that  the  maximum 
stress  is  at  the  edge  of  the  column  head,  and  we  may  assume 
the  "critical  section"  as  on  this  line.  The  exact  location  of  the 
liile  of  maximum  moment  is  indeterminate.  Under  ordinary 
conditions  it  appears  fair  to  assume  its  location  as  within  the  col- 
umn head,  a  distance  equal  to  the  thickness  of  the  slab.  There- 
fore, Mf  is  figured  for  a  value  of  r^Vo+L  In  figuring  this  mo- 
ment, values  of  the  constants  Cg  and  C«  should  be  taken  from  the 
curves  in  Figs.  3  and  4.  As  in  an  ordinary  fixed  beam,  this  bend- 
ing moment  is  negative,  so  that  the  upper  side  of  the  slab  is  in 
tension  and  the  lower  in  compression.  Having  found  the  moment, 
the  design  of  the  reinforcement  and  the  thickness  of  the  slab  may 
be  worked  out  as  for  an  ordinary  beam. 

The  curves  in  Figs.  5  to  8  inclusive  will  be  found  of  assistance 
in  working  out  the  design. 

Reinforcement  in  Column  Head.* 

The  slab  at  the  column  head  might  be  designed  with  the 
reinforcement  all  in  the  top  of  the  slab  running  in  four  directions 
provided  the  slab  is  thick  enough  so  that  the  concrete  will  not  be 
overstressed  in  compression.  In  order  to  reduce  the  thickness  of 
the  slab  and  therefore  save  the  additional  cost  and  weight  of  con- 
crete over  the  entire  floor,  it  is  economical  to  place  reinforcement 
in  the  bottom  of  the  slab  as  well  as  the  top,  and  figure  it  as  assist- 
ing the  concrete  to  take  compression.  Since  a  portion  of  the 
bars  need  to  extend  only  far  enough  beyond  the  column  head  to 
furnish  suitable  bond,  the  cost  of  this  additional  reinforcement 
will  be  much  less  than  the  cost  of  an  additional  thickness  of  con- 
crete over  the  entire  slab.  The  tensile  reinforcement  must  not 
sag  over  the  column  head. 

To  make  it  easy  to  place  the  concrete  and  also  to  bring  the 
center  of  gravity  of  the  reinforcement  as  near  to  the  surfaces  of 
the  slab  as  possible  in  order  to  give  the  longest  moment  arm  and 

*  Certain  features  of  flat  slab  reinforcement  are  covered  by  patents  of  C.  A.  P.  Turner. 


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Thompson  on  Design  of  Concrete  Flat  Slabs.       263 

thus  a  thinner  slab,  two  layers  of  reinforcement  may  be  placed 
in  the  top  of  the  slab  and  two  layers  in  the  bottom.  The  relation 
of  the  quantity  in  the  top  and  bottom  must  be  determined  by  the 
design.  If  a  thin  slab  is  desired,  even  more  reinforcement  may 
be  placed  in  the  bottom  than  the  top.  In  the  tables,  three  ratios 
of  reinforcement  are  given  and  the  percentages  selected  are  those 
that  will  give  the  required  working  stresses  in  the  concrete  and 
the  reinforcement. 

The  Minneapolis  test  already  referred  to  shows  that  not 
only  the  remforcement  directly  over  the  column  head,  but  the 
reinforcement  for  a  considerable  distance  each  side  takes  tension. 
In  view  of  this  test  and  of  the  tests  made  at  the  University  of 
Illinois*  it  is  safe  to  assume  that  the  reinforcement  may  be  spaced 
over  a  distance  at  least  equal  to  the  diameter  of  the  column  head 
plus  three  times  the  thickness  of  the  slab. 

The  determination  as  to  whether  the  diagonal  or  rectangular 
reinforcement  should  be  placed  at  the  top  is  governed  by  the 
relative  quantities  of  each.  More  reinforcement  is  required  for 
the  diagonal  direction  through  the  slab,  hence  the  layers  which 
are  largest  in  section  may  be  run  diagonally. 

Agreement  with  Minneapolis  Tests. 

By  our  theory  it  is  possible  to  compute  the  stresses  not  only 
next  to  the  column  head  but  at  any  point  in  the  slab.  In  several 
cases,  knowing  the  exact  location  of  the  points  where  the  deform- 
ations were  measured  in  the  Minneapolis  tests  the  stresses  at 
these  points  have  been  computed.  Using  5.6  in.  as  the  moment 
arm,  and  including  the  radial  bars  as  assisting  to  take  tension, 
the  maximum  stress  in  the  reinforcement  over  the  edge  of  the 
column  is  26,000  lb.  per  sq.  in.  under  the  normal  load  of  225  lb. 
per  sq.  ft.  as  compared  with  20,700  lb.  per  sq.  in.  given  by  Mr. 
Lord  as  the  actual  maximum  stress  in  the  floor.  This  is  no  greater 
diflference  than  there  ought  to  be  between  design  and  test  and 
shows  our  method  to  be  slightly  more  conservative  than  the 
actual  test. 

The  compression  in  the  concrete  is  more  difficult  to  check 
since  the  exact  locations  of  the  test  points  are  not  given.   Com- 

♦  See  paper  on  *'  A  Test  of  a  Flat  Slab  Floor  in  a  Reinforced  Concrete  Building."  by  Arthur, 
R.  Lord,  Proceedingt,  Vol.  VII.  page  182. 


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264      Thompson  on  Design  of  Concrete  Flat  Slabs. 

putations,  however,  show  unquestionably  that  our  methods  are 
conservative  enough  to  allow  for  the  irregularities  in  concrete 
mixtures,  and  the  danger  of  not  having  perfect  concrete  at  the 
critical  section. 

Moment  at  Center  of  Slab. 

It  is  possible  to  adapt  the  Eddy  theory  to  the  design  of  the 
center  of  the  slab  as  well  as  to  the  supports.  In  practical  design, 
however,  as  has  been  indicated,  the  thickness  of  the  slab  is  deter- 
mined by  the  thickness  at  the  support,  which  is  always  the  greater. 
But,  in  order  to  avoid  too  wide  spacing  of  the  bars  and  to  adapt 
the  center  reinforcement  to  that  over  the  supports,  more  bars 
are  generally  run  through  the  slab  than  the  results  of  tests  would 
show  to  be  necessary.  Consequently,  instead  of  considering  this 
from  a  theoretical  standpoint  alone,  safe  values  for  the  bending 
moments  may  be  selected,  based  on  general  principles  of  mechanics 
and  qualified  by  actual  tests. 

Let  Ii«  distance  between  lines  of  inflection.  This  distance 
will  be  about  7  of  the  net  span  between  column  heads. 

For  the  rectangular  reinforcement,  if  the  slabs  between  the 
points  of  inflection  were  simply  supported,  we  should  have  a 
moment  of  wli/8.  However,  the  bending  moment  in  the  Minne- 
apolis tests,  based  on  the  maximum  stresses  under  imif orm  work- 
ing load,  is  about  wli/ZZ.  It  would  appear  amply  safe,  therefore, 
to  adopt  a  value  of  M^wli/\2, 

For  the  diagonal  reinforcement,  the  bars  run  in  two  direc- 
tions, and  considering  both  theory  and  test,  a  value  of  M=wli^/24t 
is  conservative  to  use  for  the  reinforcement  in  each  direction. 

Cross  Reinforcement  Between  Columns. 

In  flat  slab  floors  cracks  are  apt  to  occur  between  colimms  on 
rectangular  lines,  because,  since  the  span  is  shorter,  the  deflection 
is  less  than  in  the  center  of  the  slab.  To  prevent  these  cracks,  it 
is  advisable  to  place  cross  reinforcement  of  small  bars  in  the  top  of 
the  slab. 

Tables  for  Design  of  Slabs. 

Tables  I-IV  give  thicknesses  of  slab,  reinforcement  and 
size  of  column  head  for  various  column  spacings  and  loads. 


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Design  of  Concrete  Flat  Slabs.      265 


OJO  ai5    020     025  030    035    040    QA5    0,50    055  060 
Valued    of  Constant     Cc 
a>0.10 


040   0.15    0^0    ass    0,30    0-35    040   0.4-S    0-50   a55  050 
Valuer     of    Cons+anf    Cc 
a.  0.15 

FIG.    5. — ^DIAGRAM    GIVING    VALUES    OF    CONSTANTS   IN   FORMULA 
/c"^-r^    FOR    a  =0.10    AND     0.15 

Depth  of  Reinforcement  in  Compression.  Area  of  Reinforcement  in  Tension. 

Q  Ml  pas 

Depth  of  Reinforcement  in  Tension.  Area  of  Concrete  above  Reinforcement. 


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266 


Thompson  on  Design  of  Concrete  Flat  Slabs. 


OiO  OJS    OJZO    a25   O^Q    035   040   045    0^0    055  a60 
Vdlues   of  Con3+cint     Cc 
a*0.ao 


0.04a 


aiO    OJS    0^0    0.^5   030    0.aS  ft40   a45    050    055  0.60 
Vdlues     of   Cons+cinf    Cc 
a=0.a5 

FIG.  6. —  DIAGRAM    GIVING    VALUES    OP    CONSTANTS    IN    FORMULA 

/c"^,^  FOR  a =0.20  AND  a  =0.25 

Depth  of  Reinforcement  in  Compression.  Area  of  Reinforcement  in  Tension. 

Depth  of  Reinforcement  in  Tension.  Area  of  Concrete  above  Reinforcement. 


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Thompson  on  Design  op  Concrete  Flat  Slabs.       267 

Three  arrangements  for  reinforcement  over  the  column  head 
are  chosen:  The  first  where  the  area  of  reinforcement  in  the  top 
is  twice  the  area  of  reinforcement  in  the  bottom;  the  second 
where  the  two  are  equal;  and  the  third  where  the  area  of  rein- 
forcement in  the  bottom  is  one  and  a  half  times  that  in  the  top. 
This  gives  the  designer  a  variety  of  thicknesses  of  slab.     The 


aio  ais  020  0.25  oao  035  C40  045  050  055  ojbo 

Votued    of  Cone+Gin+    C© 

FIQ.    7. — DIAGRAM    GIVING    VALUES    OF   CONSTANTS   IN    FORMULA 

M 


/*-; 


FOR  a  "0.30 


a"> 


P- 


Cch^ 

Depth  of  Reinforcement  in  Compression. 
Depth  of  Reinforcement  in  Tension. 
Area  of  Reinforcement  in  Tension. 
Area  of  Concrete  above  Reinforcement. 


percentages  of  reinforcement  selected  are  those  which  produce, 
with  the  given  conditions,  a  compressive  stress  of  800  lb.  per 
sq.  in.  in  the  concrete  and  16,000  lb.  in  the  reinforcement.  In 
order  to  allow  800  lb.  in  the  concrete,  it  should  be  mixed  in  pro- 
portions as  rich  as  1  part  cement  to  2  parts  fine  aggregate  to  4 
parts  coarse  aggregate.  Poisson's  ratio  is  assumed  as  0.1,  which 
from  recent  tests  appears  to  be  a  fair  value. 


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268      Thompson  on  Design  of  Concrete  Flat  Slabs. 

The  size  of  column  head  has  been  figured  for  a  shear  of  60  lb. 
per  sq.  in.  on  a  circle  a  distance,  t,  (the  thickness  of  slab)  outside 
of  the  column  head.  This  shear  is  used  simply  as  a  measure  of  the 
diagonal  tension.  The  value  is  somewhat  larger  than  is  permitted 
in  beam  design  but  appears  to  be  warranted  in  the  case  of  flat  slabs. 

a040r 


ooos 


0,04(1 


Valuer    of  Conatan+    C^ 


no.  8. — ^DIAGRAM  GIVING  YALUBS  OF  C0N8TANTB  IN  FOBlfTTIiA 

Depth  of  Reiaforcement  in  Compression. 
Depth  of  Reinforcement  in  Tension. 
Area  of  Reinforcement  in  Tension. 


P  = 


Area  of  Concrete  above  Reinforcement. 


The  reinforcement  in  the  center  of  the  slabs  has  been  figured 
for  a  stress  of  16,000  lb.  per  sq.  in. 

Diagrams  for  Designing  Slabs. 

To  provide  for  cases  not  covered  by  the  tables,  curves  for 
values  of  Cg  and  C,  are  given  so  that  the  moment  under  various 
conditions  can  be  readily  figured  from  the  formula  for  the  bending 
moment  given  above. 


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Thompson  on  Design  op  Concridtb  Flat  Slabs.       269 

Diagrams   for  Determining   Reinforcement  in   Top 
AND  Bottom  of  Beams  or  Slabs. 

In  Figs.  5  to  8  curves  are  plotted  for  finding  the  values  of 
the  constants  C^  and  C,  in  the  formulas  for  the  reinforcement  and 
concrete  stresses  in  beams  or  slabs  with  reinforcement  in  top 
and  bottom.  The  curves  are  drawn  for  diflferent  values  of  a, 
the  ratio  of  depth  of  reinforcement  in  compression  to  depth  of 
reinforcement  in  tension,  and  for  diflferent  values  of  pVP>  where 
p  =  ratio  of  cross-section  of  reinforcement  in  tension  to  concrete 
above  it*,  and  p^  ^  ratio  of  crossHsection  of  reinforcement  in 
compression  to  this  same  area  of  concrete. 

EXAMPLB. 

Example. — ^For  a  warehouse  floor  with  a  live  load  of  150 
lb.  per  eq.  ft.  and  a  column  spacing  of  20  ft.  each  way,  what  is 
the  necessary  thickness  of  slab,  size  of  column  head,  and  amount 
of  reinforcement? 

Sohdian. — ^From  Table  II  the  thickness  of  slab  is  given  as 
8}  in.,  the  size  of  column  head  as  5.5  ft.,  and  the  area  of  rein- 
forcement as  24.7  sq.  in.  at  top  of  slab  and  same  amount  at  bottom 
of  slab  over  column,  using  ratio  of  area  of  reinforcement  in  ten- 
sion to  area  of  concrete  below  as  0.017.  Dividing  these  values 
by  4,  as  each  end  of  the  bands  is  effective,  we  have  24.7/4  =  6.2 
sq.  in.  as  the  area  of  reinforcement  in  each  band.  For  this  may 
be  used  twenty  |-in.  round  bars  spaced  5  in.  center  to  center  for 
both  tension  and  compression  reinforcement. 

The  amount  of  reinforcement  required  at  center  of  rectangular 
band  is  0.17  sq.  in.  per  ft.  of  width.  Placing  a  f-in.  round  bar 
every  10  in.  gives  more  than  the  necessary  area,  but  ease  in  plac- 
ing the  reinforcement  makes  up  for  the  extra  amount.  The 
amount  required  at  center  of  diagonal  band  is  0.35  sq.  in.  per 
ft.  of  width.  |-in.  round  bars  every  10  in.  will  thus  give  neces- 
sary amount. 


*  Where  the  tenaile  reinforoement  ia  at  the  top,  aa  over  a  support  of  a  flat  slab  or  beam, 
the  concrete  area  is  taken  below  the  tensile  reinf oroement. 


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270      Thompson  on  Design  op  Concrete  Flat  Slabs. 

Table  I. — Design  of  Flat  Slab. 

Thickness  of  Slab,  Areas  of  Reinforcement  and  Sizes  of  Column 

Head  are  Given  for  Different  Spans  and  Percentages  of 

Reinforcement. 

LIVE  LOAD  100  LB.  PER  SQ.  FT. 


ft. 


t 


go 

< 

it) 
in. 


Q 
ft. 


•a.9 

i 

|i 


8q.  in. 


aq.  in. 


aq.  in.    aq.  in. 


12 
12 
12 

14 
14 
14 

16 
16 
16 

18 
18 
18 


22 
22 
22 


0.014 
0.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.017 
0.022 


20  0.014 
20  0.017 
20   0.022 


0.014 
0.017 
0.022 


24  0.014 
24  I  0.017 
24   0.022 


0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 


5J 

5 

4i 

5 
5i 

7i 
6i 
5i 

8i 
7i 
6i 

9i 

8i 
7i 

lOi 
9 
8 

m 

10 
8J 


2.00 
2.00 
2.50 

2.25 
2.75 
3.00 

3.00 
3.25 
3.75 

3.50 
3.75 
4.50 

4.00 
4.50 
5.00 


4.50 
4.81 
7.26 

5.94 
7.93 
9.96 

9.51 
10.95 
14.01 

12.48 
14.42 
18.67 

16.36 
19.47 
23.89 


4.50 
5.00 
5.75  I  31.05 


20.21 
I  24.05 


5.00  25.10 
5.75  I  30.41 
6.50  I  37.80 


2.25 

4.81 

10.90 

2.97 

7.93 

14.95 

4.76 
10.95 
21.05 

6.24 
14.42 
28.00 

8.18 
19.47 
35.80 

10.11 
24.05 
46.60 

12.55 
30.41 
56.60 


0.16 
0.17 
0.18 

0.19 
0.20 
0.21 

0.22 
0.23 
0.24 

0.26 
0.27 
0.28 

0.30 
0.31 
0.32 

0.34 
0.34 
0.35 

0.38 
0.39 
0.40 


0.09 
0.09 
0.09 

0.11 
0.11 
0.11 

0.12 
0.12 
0.12 

0.14 
0.14 
0.14 

0.16 
0.16 
0.15 

0.18 
0.17 
0.16 

0.20 
0.20 
0.19 


*  Area  of  reinforcement  over  column  head  » circumference  of  column  head  in  inchea 
Xd  Xp  or  p'  depending  upon  whether  the  reinforcement  is  in  tension  or  compression.  This 
reinforcement  is  assumed  as  distributed  over  the  entire  widths  of  the  bands.  Thus  if  a  band 
of  reinforcement  has  2  sq.  in.  in  section  the  area,  efTective,  for  two  bands  will  be  4  aq.  in.  (See 
example.) 


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Thompson  on  Design  op  Concrete  Flat  Slabs.       271 


Table  II. — Design  op  Flat  Slabs. 

Thickness  of  Slab,  Areas  of  Reinforcement  and  Sizes  of  Column 

Head  are  Given  for  Different  Spans  and  Percentages  of 

Reinforcement. 

LIVE  LOAD  180  LB.  PER  SQ.  FT. 


1^ 


12 
12 
12 

14 
14 
14 

16 
16 
16 

18 
18 
18 

20 
20 
20 

22 
22 
22 

24 
24t 


d  a  ^ 

■ffi 

(p) 


0.014 
0.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.016 


ml 


(pO 


0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

6.007 
0.017 
0.033 


007 
017 
033 

007 
017 


0.033 

0.007 
0.013 


iff 

ID. 


4J 

u 

5J 

5 

4i 

4} 

7i 
6i 
5i 


8i       10 

7 


:i 


< 
(0 


6 

5J 

4i 


8 

7i 

6 

8} 
7} 

61 


lOi 

8i 


n    11* 

8i       lOit 


ft. 


2.25 
2.50 
3.00 


S  o 


^1 

it 

aq.  in. 


5.64 
6.81 
8.72 


3.00  ,     8.72 

3.50  I  11.22 

3.75  I  13.22 

3.50  I  12.03 

3.75  13.83 

4.50  I  17.75 

4.00  I  15.32 

4.50  18.05 

5.50  '  24.00 

5.00  21.80 

5.50  !  24.70 

6.25  I  31.14 

5.50  I  26.15 

6.25  I  31.07 

7.00  39.24 

7.00  36.05 

7.00  36.95 


I- 

g1 


aq.  in. 


IP 

hi 


aq.  in. 


2.82  '  0.18 

6.81  0.19 

13.09  ,  0.21 

4.36  0.22 

11.22  0.23 

19.82  0.24 

6.02  '  0.26 

13.83  0.27 
26.80  0.28 


7.66 
18.05 
36.00 

10.90 
24.70 
46.70 

13.08 
31.07 
58.80 

18.03 
29.57 


0.31 
0.32 
0.33 

0.34 
0.35 
0.36 


aq.  m. 

0.10 
0.10 
0.10 

0.12 
0.11 
0.11 

0.14 
0.13 
0.13 

0.16 
0.15 
0.17 

0.17 
0.17 
0.16 


0.38  I  0.18 
0.39  0.17 
0.40    0.17 


0.42 
0.43 


0.21 
0.20 


The  values  printed  in  black  type  are  figured  for  a  column  head  7  ft.  in  diameter  and  the. 
thickncM  of  the  alab  is  increased  to  withstand  the  shear. 

*  Area  of  reinforcement  over  column  head  —  circumference  of  column  head  in  inchea  Xd  X  P 
or  pi  dei>ending  upon  whether  the  reinforcement  is  in  tension  or  compression.  This  reinforce- 
ment is  assumed  as  distributed  ovei  the  entire  widths  of  the  bands.  Thus  if  a  band  of  reinforce- 
ment has  2  sq.  in.  in  section  the  area,  effective,  for  two  bands  will  be  4  sq.  in.     (See  example.) 

t  The  thickness  of  slab  for  the  24-ft.  span  may  be  decreased  to  8}  in.  by  using  0.022  and 
0.033  ratios  of  reinforcement  and  bending  the  bars  to  resist  diagonal  tension. 


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272      Thompson  on  Design  op  Concrete  Flat  Slabs. 


Table  III. — Design  of  Flat  Slabs. 

Thickness  of  Slab,  Areas  of  Reinforcement  and  Sizes  of  Coltthn 

Head  are  Given  for  Different  Spans  and  Percentages  of 

Reinforcement. 

LIVE  LOAD  200  LB.  PER  8Q.  FT. 


I 

P 

GQ 
ft. 


h 

.-  P  2  « 
.23  !£ 

(P) 


i 


5 

.2 

i 
i 

1 


(lO 


Us 

m 


t 


So 

-< 

(0 
in. 


ft. 


2  2 


is 


0)  Q. 

as 


£a 


sq.  in. 


ill 

in 

la     I 


sq.  in. 


aq.  in. 


12 
12 
12 

14 
14 
14 

16 
16 
16 

18 
18 
18 

20 
20 
20 

22 
22 1 

24t 


0.014 
0.017 
0.02!^ 

0.014 
0.017 
0.022 

0.014 
O.017 
0.022 

0.014 
0.017 
0.022 

0.014 
0.017 
0.019 

0.014 
0.016 

0.014 


0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.033 

0.007 
0.017 
0.029 

0.007 
0.012 

0.006 


5 

4J 

3i 

6 
6 
4i 

6 
4i 

7i 

II 

9i 
8i 

lOi 


6i 
5i 
5 

7J 
6i 
6i 

8i 
7i 
6 

9 

8 
7 

lOi 
8i 
7i 

Hi 

lot 

12t 


2.50 
3.25 
3.76 

3.25 
3.75 
4.50 

4.00 
4.50 
5.50 

4.75 
5.50 
6.50 

5.50 
6.25 
7.00 

6.25 
7.00 

7.00 


6.60 

9.38 

10.37 

10.31 
12.02 
15.88 

14.26 
16.60 
21.70 

18.80 
22.92 
29.70 

24.71 
29.08 
31.35 

31.38 
34.90 

37.90 


3.30 

9.38 

15.40 

5.16 
12.02 
23.80 

7.30 
16.60 
32.55 

9.46 
22.92 
44.60 

12.36 
29.08 
47.85 

15.69 
26.15 

16.24 


0.20 
0.21 
0.23 

0.24 
0.25 
0.26 

0.28 
0.30 
0.32 

0.33 
0.34 
0.35 

0.37 
0.38 
0.39 

0.42 
0.42 

0.46 


0.10 
0.10 
0.10 

0.13 
0.12 
0.11 

0.14 
0.14 
0.14 

0.17 
0.16 
0.15 

0.18 
0.17 
0.16 

0.20 
0.19 

0.22 


The  values  printed  in  black  type  are  figured  for  a  column  head  7  ft.  in  diameter  and  the 
thickness  of  the  slab  increased  to  withstand  the  shear. 

*  Area  of  reinforcement  over  column  head— circumference  of  column  head  in  inches 
Xd  Xp  or  p'  depending  upon  whether  the  reinforcement  is  in  tension  or  compression.  This 
reinforcement  is  assumed  as  distributed  over  the  entire  widths  of  the  bands.  Thus  if  a  band 
of  reinforcement  has  2  sq.  in.  in  section  the  area,  effective,  for  two  bands  will  be  4  sq.  in.  (Seo 
example.) 

t  The  thickness  of  slabs  for  the  22-  and  24-ft.  spana  may  be  decreased  to  BH  u^*  i^d  9H 
in.  respectively,  by  using  0.022  and  0.033  ratios  of  reinforcement  and  bending  the  bars  to  i 
diagonal  tension. 


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I^OMPSON  ON  Design  of  Concrete  Plat  Slabs.       273 

Table  IV. — ^Design  of  Flat  Slabs. 

Thickness  of  Slab,  Areas  of  Reinforcement  and  Sizes  of  Column 

Head  are  Given  for  Different  Spans  and  Percentages  of 

Reinforcement. 

LIVE  LOAD  300  LB.  PER  SQ.  FT. 


•s 

)n  of  re- 
ompres- 
!   below 
tension. 

1 
n  head.  I 

rcement 
tension. 

1 

int  over 
ireasion. 

IP 
III 

8^ 

lag-: 
his 

1^ 

1 

is 

6 

a 

is 

2*-    1 

em 

2  -^      a 

CQ 

!•§:§ 

(d) 

< 

1 

eS 

s 

1^ 

°.2 

< 

• 

He! 

ft. 

(p) 

(p') 

in. 

in. 

ft. 

sq.  in. 

sq.  in. 

sq.  in. 

sq.    n. 

12 

0.014 

0.007 

5i 

6} 

3.50 

9.72 

4.86 

0.24 

0.12 

12 

0.017 

0.017 

4i 

5i 

4.25 

12.27 

12.27 

0.25 

0.11 

12 

0.022 

0.033 

31 

5 

5.00 

15.56 

23.30 

0.26 

0.10 

14 

0.014 

0.007 

61 

7} 

4.25 

14.03 

7.02 

0.29 

0.13 

14 

0.017 

0.017 

5i 

6i 

5.00 

16.84 

16.84 

0.30 

0.12 

14 

0.022 

0.033 

4i 

5i 

6.00 

21.18 

31.72 

0.31 

0.11 

16 

0.014 

0.007 

7 

8i 

5.00 

18.48 

9.24 

0.33 

0.15 

16 

0.017 

0.017 

6 

7J 

6.00 

23.10 

23.10 

0.35 

0.15 

16 

0.022 

0.033 

5 

6i 

7.00 

29.05 

43.50 

0.35 

0.12 

18 

0.014 

0.007 

7i 

9i 

6.00 

24.59 

12.30 

0.39 

0.17 

18 

0.017 

0.017 

6i 

8 

7.00 

29.18 

29.18 

0.40 

0.16 

18 

0.015 

0.015 

61 

8i 

7.00 

26.74 

26.74 

0.39 

0.15 

20 

0.014 

0.007 

81 

10} 

7.00 

32.32 

16.16 

0.43 

0.19 

20t 

0.015 

0.011 

8} 

lOit 

7.00 

33.65 

25.36 

0.43 

0.18 

22t 

0.012 

0.003 

10} 

12it 

7.00 

32.61 

8.23 

0.47 

0.22 

24t 

0.010 

0.000 

13i 

ISit 

7.00 

35.64 

0.00 

0.51 

0.25 

The  values  printed  in  black  type  are  figured  for  a  column  head  7  ft.  in  diameter  and  the 
thickness  of  the  slab  increased  to  withstand  the  shear. 

•Area  of  reinforcement  over  column  head  =  circumference  of  column  head  in  inches 
X<f  Xp  or  p'  depending  upon  whether  the  reinforcement  is  in  tension  or  compression.  This 
reinforcement  is  assumed  as  distributed  over  the  entire  widths  of  the  bands.  Thus  if  a  band 
of  reinforcement  has  2  sq.  in.  in  section  the  area,  effective,  for  two  bands  will  be  4  sq.  in.  (See 
example.) 

fThe  thickness  of  slabs  for  the  20-.  22-  and  24-ft.  spans  may  be  decreased  to  8>i  in..  9H 
in.  and  11  in.  respectively,  by  using  0.022  and  0.033  ratios  of  reinforcement  and  bending  the 
bars  to  resist  diagonal  tension. 


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DISCUSSION 


Mr.  Lindau.  Mr.  Alfred  E.  Lindau. — Regarding  this  method  of  design- 

ing a  flat  slab  or  plate  of  concrete  it  might  be  of  value  to  note 
that  the  analysis  is  based  on  the  assumption  that  there  exists 
a  line  of  contra-flexure  around  the  colmnn  substantially  circular 
in  form  and  near  the  quarter  point  of  span,  that  the  balance  of 
the  span  is  supported  along  this  line  and  that  consequently  there 
is  no  stress  in  any  direction  along  this  line.  There  is  some  ques- 
tion as  to  this  line  of  contra-flexure,  in  fact  there  is  some  evidence 
to  show  that  instead  of  a  line  of  contra-flexure  there  exist  per- 
haps only  four  points  where  there  is  no  stress  in  any  direction. 
If  such  is  the  case  the  analysis  would  be  entirely  diflFerent  from 
that  which  has  been  outlined. 

Mr.  Andenon.  Mr.  W.  P.  Anderson. — One  of  the  important  things  in 
designing  a  flat  slab  has  not  been  touched — ^the  bending  moment 
on  the  exterior  column.  I  think  that  has  an  effect  on  the  thick- 
ness of  the  slab.  The  thicker  the  slab,  it  appears  to  me,  the  less 
that  bending  moment  would  be.  I  have  not  gone  into  the  matter 
thoroughly  enough  to  determine  how  the  bending  moment  of 
the  exterior  column  is  to  be  figured,  but  it  seems  to  me  that  it  is 
the  critical  point  in  the  design  of  the  flat  slab  and  one  that  has 
not  yet  been  touched  upon  enough  by  those  who  have  given  the 
subject  thought.  This  point  in  the  design  of  the  flat  slab  has 
not  been  covered  in  the  tests  made  on  the  flat  slabs.  They  have 
been  made  in  the  center  of  the  building  and  the  exterior  colimm 
has  not  been  tested  at  all  to  see  what  the  moment  is.  It  is  some- 
thing that  ought  to  be  covered.  I  am  not  prepared  to  say  how 
it  ought  to  be  taken  care  of,  but  I  believe  it  ought  to  be  looked 
into. 

Mr.  Lindau.  Mr.  Lindau. — The  test  covered  in  Part  II  of  the  report  of 

the  Committee  on  Reinforced  Concrete  refers  to  an  end  or  wall 
panel.  In  fact,  it  was  a  building  with  one  line  of  colimms  making 
all  panels  end  panels,  so  to  speak. 

Mr.  Green.  Mr.  HERBERT  P.  Green. — I  have  been  experimenting  a 

little  bit  this  last  year  on  flat  slabs  of  a  different  construction 

(274) 


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Discussion  on  Concrete  Plat  Slabs.  275 

from  any  others  I  have  seen.  Realizing  that  the  shear  around  Mr.  Green, 
the  head  of  the  column  is  the  greatest  thing  to  be  considered,  I 
endeavored  to  work  out  a  way  of  thickening  the  slab  at  this  point 
and  have  succeeded  in  obtaining  a  flat  ceiling  without  the  flar- 
ing head.  We  have  built  one  building  by  this  system  and  tested 
it  and  it  is  a  perfect  success. 

The  reinforcing  bars  run  directly  and  diagonally  from  col- 
umn to  column.  The  bending  moment  on  each  beam  is  considered 
as  coming  from  the  load  of  one-fourth  of  the  panel,  which  posi- 
tively occurs  because  triangles  are  formed  in  between  the  direct 
and  diagonal  girders  which  are  filled  with  ordinary  stock  tile. 
Between  these  tile  are  concrete  joists,  supported  by  the  beams. 
This  construction  can  be  figured  by  any  engineer  without  em- 
pirical formulas. 

At  the  center  of  the  slab  between  the  columns  on  the  diagonal 
girders  in  the  bottom  or  top  of  the  slab,  supplementary  rein- 
forcement can  be  placed,  but  it  is  generally  not  necessary.  Every 
beam  and  every  girder,  or  every  joist  and  every  beam,  as  they 
may  be  called,  is  of  a  T-section,  the  concrete  above  the  tile  form- 
ing the  flange  of  the  direct  and  diagonal  beams  and  the  supple- 
mentary joists  in  the  triangles,  so  that  the  analyses  of  the  stresses 
in  this  slab  are  very  easy,  according  to  the  ordinary  theories  of 
design. 

Mr.  Lindau. — I  would  like  to  ask  Mr.  Green  whether  in  Mr.Lindau. 
his  method  of  flat  slab  construction  he  has  made  joints  along 
these  triangles,  so  that  the  tile  filler  is  disconnected  absolutely 
from  the  balance  of  the  slab  thereby  making  separate  beams, 
or  whether  it  is  all  concreted  in  and  becomes  a  portion  of  the 
slab  as  a  whole. 

Mr.  Green. — ^The  tile  actually  becomes  a  portion  of  the  Mr.  Green, 
slab,  but — according  to  the  methods  generally  used  for  figuring 
the  efficiency  of  tile  joist  construction — the  tile  is  considered  as 
nothing  but  a  core,  so  that  the  concrete  construction  is  the  prin- 
cipal thing  considered.  If  we  should  remove  the  tile,  in  this 
construction  it  would  be  the  same  thing  as  removing  it  in  any 
tile  joist  construction,  L  e.,  we  would  have  a  floor  with  ribs  or 
stiffeners  below,  and  in  this  case  they  would  be  in  four  directions 
from  column  to  column,  with  supplementary  stiffeners  in  the 
triangles.    The  tile  is  simply  a  form. 


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276  Discussion  on  Concrete  Flat  Slabs. 

Mr.  xjadaii.  Mr.   Lindau. — I   take  exception  to  the  assumption  that 

you  have  a  series  of  beams  that  are  free  and  independent  to  act 
as  beams;  because  just  as  soon  as  you  connect  up  the  slab  so  as 
to  have  anything  resembling  a  homogeneous  structure  you  have 
changed  the  stress  condition  from  a  slab  to  a  beam.  The  loads 
are  transmitted  by  bending  moment  or  transverse  stresses,  or  a 
combination  of  those  two;  you  cannot  draw  imaginary  diagonals 
or  anything  on  that  slab  and  say  that  this  is  the  direction  in 
which  the  load  will  travel.  The  load  will  travel  along  the  lines 
of  relative  rigidity  of  the  structure  and  you  cannot  make  it  go 
in  one  direction  rather  than  another  unless  the  slab  is  built  accord- 
ingly. This  is  the  difficulty  with  most  theories  and  methods  of 
strip  analysis,  where  the  freedom  of  the  slab  is  tied  up  in  various 
ways  and  consequently  cannot  be  separated  into  the  various 
elements  it  may  be  considered  to  be  made  up  of. 

Mr.  orMn.  Mr.  Green. — ^That  may  be  so,  but  in  the  two-way  reinforced 

concrete  floor  with  tile  fillers  one  figures  the  loads  are  carried 
through  the  joists,  which  are  supported  on  the  beams,  to  the 
beams  which  run  directly  between  the  columns.  Now  I  simply 
make  two  more  beams  or  headers  in  the  slab.  I  have  run  them 
diagonally  across  from  column  to  column  and  the  joists  in  the 
triangles  between  the  direct  and  diagonal  beams  are  supported 
by  these  direct  and  diagonal  beams.  It  is  the  same  principle 
that  would  occur  in  a  wooden  framed  structure  with  diagonal 
beams,  except  that  we  have  a  T-section  in  all  directions  and 
the  stresses  in  the  concrete  above  and  below  the  neutral  axis 
at  any  point  can  be  figured  just  as  readily  as  in  the  two-way 
reinforced  concrete  floor. 


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THE  DESIGN  OF  CONCRETE  GRAIN  ELEVATORS. 

By  E.  Lee  Heidenreich.* 

During  the  International  Congress  of  Engineers  in  1893,  at 
Chicago,  III.,  I  was  appointed  by  the  American  Society  of  Civil 
Engineers  to  present  a  paper  on  '*  American  Grain  Elevators," 
having  at  that  time  had  about  ten  years'  experience  in  the  con- 
struction and  erection  of  grain  elevators  in  North  and  South 
America.  Elevators  at  that  time  had  the  same  functions  as  they 
have  today  and  may  as  a  rule  be  divided  into  certain  classes: 

1.  Farmers'  elevators  or  small  station  elevators  with  a 
capacity  from  5000  to  50,000  bushels — ^where  the  farmers  would 
deliver  their  grain  in  wagon  loads,  up  to  5  tons  capacity,  have 
it  weighed,  elevated  and  shipped  out  in  railroad  cars. 

2.  Mill  elevators  or  cleaning  elevators,  built  as  adjuncts 
to  flour  mills,  within  varying  capacities  from  50,000  to  500,000 
bushels  and  containing,  besides  receiving  and  shipping  apparatus, 
scales  and  cleaning  machinery. 

3.  Terminal  elevators,  divided  into  storage  and  working 
houses.  The  working  houses  would  receive  the  grain,  weigh 
and  ship  it  into  the  storage  elevators  or  cars.  The  storage 
elevators  would  merely  be  for  the  purpose  of  storing  grain. 

4.  Transfer  elevators  located  at  prominent  points  where 
different  grains  are  graded  and  changed  from  one  grade  to 
another  and  shipped  from  western  to  eastern  cars. 

5.  Marine  elevators,  where  the  grain  would  either  be  received 
from  canaJ  boats  or  vessels  or  shipped  into  them.  These 
elevators  are  either  dock  elevators  or  floating  elevators. 

Up  to  1893  there  were  no  reinforced  concrete  grain  elevators 
in  the  United  States.  At  that  time  two  large  grain  elevators 
were  imder  construction  at  Galatz  and  Braila,  Roumania,  and 
Mr.  Herman  0.  Schlawe,  a  representative  of  the  Roumanian 
government,  sent  over  to  see  how  we  handled  grain  and  took  care 
of  oiu"  grain  elevators,  showed  me  the  plans  of  the  same  elevators 
designed  by  Luther  of  Braimschweig,  Germany.     These  elevators 

^Consulting  Engineer.  Kansas  City,  Missouri. 

(277) 


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278        Heidbnreich  on  Concrete  Grain  Elevators. 

were  of  unit  construction,  somewhat  similar  to  the  one  described 
by  Mr.  Darnell,*  excepting  that  the  bins  were  honeycombed 
hexagonal  cells,  built  of  flat  slabs  3  ft.  square,  and  comer  pieces, 
all  interlocked.  They  were  all  built  on  the  ground,  erected  and 
interlocked  somewhat  similar  to  tile  construction.  The  difficulty 
with  flat  slab  walls  was,  of  course,  that  they  were  subject  to 
direct  flexion,  and  therefore  became  quite  cumbersome,  owing  to 
the  lateral,  rather  heavy  pressure  in  grain  bins,  and  were  only 
suitable  for  bins  of  small  dimensions. 

Steel  tanks  have  been  tried  in  this  country,  but  there  was 
more  or  less  sweating  of  the  tank,  which  to  some  extent  damaged 
the  grain.  Circular  reinforced  concrete  tanks  were  then  designed, 
using  the  space  between  the  tanks  whereby  considerable  economy 
of  ground  area  was  effected  as  compared  with  isolated  tanks  and 
thereby  increasing  their  combined  strength  and  carrying  capacity 
on  the  soil  or  the  sub-structure.  The  introduction  of  the  new 
design  was,  however,  exceedingly  difficult. 

The  owners  thought  the  tanks  would  sweat  and  damage  the 
grain  and  builders  thought  the  tanks  would  surely  burst.  From 
1896  to  1899  I  designed  some  scores  of  cluster  tank  elevators  and 
presented  them  to  millers  and  grain  elevator  owners  entirely  in 
vain,  imtil  in  1899,  Frank  H.  Peavey,  of  Minneapolis,  as  an 
experiment  built  a  tank  23  ft.  in  diameter  130  ft.  high,  filled  it 
with  grain  and  found  that  it  held  grain  without  spoiling.  He  then 
sent  some  representatives  over  to  Europe  to  see  what  effect 
grain  storage  in  reinforced  concrete  had  in  Europe;  they  examined 
the  tanks  and  grain  elevators  at  Galatz  and  Braila,  in  Roumania, 
and  came  back  with  a  report  which  resulted  in  the  construction, 
in  1901,  of  a  large  one  million  and  a  half  bushel  elevator  in 
Duluth.  In  the  meanwhile  I  had  built,  in  1900,  a  cement  storage 
elevator  at  South  Chicago,  consisting  of  four  tanks  25  ft.  in 
diameter  and  56  ft.  high,  clustered  in  such  manner  as  to  utilize 
the  space  between  them. 

It  must  be  remembered  that  wheat  weighs  50  lb.  per  cu.  ft. 
while  cement  weighs  100  lb.;  and  the  fact  that  a  cement  tank  with 
5-in.  walls  at  the  top  and  7-in.  at  the  bottom,  25  ft.  in  diameter, 
would  hold  cement,  went  a  long  step  towards  convincing  people 
that  it  was  safe  to  store  grain  in  circular  tanks  and  also  in  cluster 

*  See  p.  4G4.— Ed. 


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Heidenr£ich  on  Concrete  Grain  Elevators.        279 

tanks.  The  tanks  in  South  Chicago  were  erected  on  top  of 
reinforced  concrete  girders,  which  in  turn  rested  on  columns, 
thus  forming  a  working  house  underneath  where  the  bagging  of 
the  cement  took  place. 

Since  that  time  cluster  tanks  have  grown  up  like  mushrooms 
all  over  this  country,  Canada,  South  America  and  Europe. 
There  are  upwards  of  60,000,000  bushels  capacity  built  in  the 
United  States  alone  to-day  and  they  are  being  built  in  every 
part  of  the  country  for  terminal  elevators  and  largely  for  milling 
elevators,  giving  safe  and  good  storage  and  eliminating  the  ques- 
tion of  insurance  and  the  calamity  due  to  fire  or  burning  up  of 
the  storage  plant. 

The  design  of  reinforced  concrete  grain  elevators,  consisting 
of  circular  tanks,  has  been  carefully  studied.  It  is  of  course 
entirely  a  function  of  the.  grain  pressure  in  rest  and  in  motion. 
Experiments  and  calculations  have  been  made  by  a  number  of 
well-known  engineers.  Janssen,  Wilfred  Airy,  Tolz,  Prante, 
Jameson  of  Canada  and  Milo  B.  Ketchimi,  have  all  made  experi- 
ments and  developed  formulas  whereby  the  grain  pressure  may 
be  determined  at  the  different  heights  of  the  bin.  Grain  is  not 
like  a  liquid — ^Professor  Ketchum  calls  it  a  semi-liquid, — the 
pressure  line  forms  a  curve. 

Inasmuch  as  Janssens'  solution  tallies  very  closely  with 
Jameson's  experiments,  we  niay  write  the  lateral  pressure 


and  the  vertical  pressure 


Cm' 


^(■-"  * ) 


Where  ty= the  weight  per  cu.  ft.  of  grain  or  50  lb.  for  wheat, 
jB=bin  area  divided  by  its  perimeter  (hydraulic  radius), 
ft' = the  coefficient  of  friction  of  grain  against  bin  surface; 
A=the  height  of  the  bin,  and 

C=the  ratio  between  the  lateral  and  the  vertical  pressure; 
e  =  being  the  base  of  the  Naperian  logarithm  or  2.71828. 

According  to  Jameson  for  wheat  C=0.6  and  for  grain  on 
concrete  ft' =0.4  to  0.425. 


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Heidenbeich  on  Concrete  Grain  Elevators. 


For  quick  and  easy  calculation  the  lateral  pressure  per  sq. 
ft.^qwh,  where  q  is  the  ratio  of  grain  pressure  to  liquid  pressure 
and 

F--^ -1.667  gwA 
Fig.  1  shows  the  value  of  q  for  different  ratios  of  height 
WHEAT  PRESSURES  IN  GRAIN  BINS- 


\23^5ST6B\0 


PIG.  1. — VALUES  OP  Q  POB  DIPPBRENT  RATIOS 
OP  HEIGHT  TO  DIAMETER  OP  BIN. 

divided  by  the  diameter  or  width  ^-r.     The  maximum  bottom 

h 
pressure  occurs  when  t  =3.6. 

Fig.  2  shows  a  series  of  circular  bins  with  intervening  spaces. 
The  lateral  pressure  per  sq.  ft.  of  the  grain  in  a  circular  bin  at  a 
depth  h  is  equal  to 

L^qwh 


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281 


and  the  tension  in  the  reinforcement  reqxiired  for  1  ft.  in  height  is 


The  reinforcement  area  in  sq.  ins. 
where  /«  is  the  working  stress  of  the  reinforcement  per  sq.  in. 


WIQ.  2.-HSEBIBB  OF  CIRCULAR  BINS. 

If,  however,  -the  circular  bin  is  empty  and  the  two  opposite 
interstices  A  and  B  filled,  we  have  a  condition  as  shown  in  Fig.  3 
where  it  is  quite  apparent  that  instead  of  single  reinforcement  of 
the  bin,  there  should  be  reinforcement  both  at  the  intrado  and 
extrado  of  the  ring. 

Compression  in  the  direction  A  B  clearly  causes  tension  at 


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Heidenreich  on  Concrete  Grain  Elevators. 


the  extrado  at  C  and  Z>,  and  at  the  intrado  A  and  B,  From 
experiments  in  loading  culvert  pipe  firmly  supported  at  the  two 
lower  quarter  points  corresponding  to  E  and  F,  the  maximum 
moment  may  approximately  be  written  (Fig.  4) : 


.s^^t- 


FIG.   3. — PLAN  OF  CIRCULAR  BIN. 

The  usual  formula  for  the  resisting  moment  is 

M«/C6d«andX«iM(l-|)=p/,(l.|) 

where 

/,  and  /c  the  unit  stresses  in  reinforcement  and  in  concrete. 


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Heidenreich  on  Concrete  Grain  Elevators. 


283 


The  stress  in  the  concrete  or  in  the  reinforcement  may  be 
expressed  by 


-5'('-l) 


bd* 


■('-!) 


bd* 


By  adding  1  in.  to  di  or  (is,  the  ring  thickness  is  found. 

Example:  The  25  ft.  diameter  bins  are  80  ft.  deep  and  sur- 
romided  by  interstices,  find  the  dimensions  of  concrete  wall  and 
reinforcement  required  at  60  ft.  from  the  top. 


h     25 


H A— - 


hence 
Then 

and 


no.  4. 


9-0.23  and  L=0.23X60X60=6901b.  per  sq.  ft. 


T.m^^^^,^, 


8625 
"^•"Tfinno  **  '^^  sq.  in.  per  each  foot  high 

The  inner  and  outer  reinforcement  from  the  eflfects  of  grain 
in  the  center  bin  is 

-~  =0.27  sq.  in.  or  say  §-in.  rounds  8§  in.  on  centers 
Vertical  rods  J-in.  rounds  24  in.  on  centers  tied  to  horizontals. 


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284        Heidenbeich  on  Concrete  Grain  Elevators. 

For  external  pressure  we  have 

^  -  59  -6  hence  g  "0.1  andL^O.lX  50X  60-300  lb.  per  eq.  ft. 
0       10 

(^  -o)  L'D'     C-?^,  -6)  300X  26  X  12 

jif  .  W2 L =  Vl._41_/ 18700  in.  lbs. 

64  64 


^      ^         / 18700'         /  18700      __^. 
*"*'\ibXl2  "\  110X12" ^•^^'"• 

hence  the  wall  should  be  5  m.  thick. 

18700 
'^•*'  0r8fiy^l6o6oS^4  ""^-^^  ^^-  ^^'  ^^^  ^^^»  ^^^^  extrado  and  intrado, 

showing  that  the  stresses  from  the  filled  interstices  are  greater 
than  those  resulting  from  the  filled  circular  bins.  Some  con- 
tractors using  single  reinforcement  in  the  center  bins  have  rodded 
the  interstices,  others  increase  the  thickness  of  the  bin  walls  and 
the  connection  between  contiguous  circular  bins. 

The  logical  method,  would,  however,  seem  to  be  to  use  double 
reinforcement,  a  practice  the  author  invariably  prefers  for  circular 
culverts. 

As  to  the  calculation  of  square  bins,  this  is  a  simple  matter, 
after  the  lateral  pressure  L  has  been  found. 

The  bending  moment  will  be  in  in.-its. 

LP 
Jl/  «  —  12,  where  Z= width  of  bin  in  feet. 


The  resisting  moment  as  before 

■V" 


M^UxJP  and  4=  ^,,, 


Area  of  reinforcement  required 

A«  =  17-;  as  before 

Interior  bin  walls  having  alternately  pressure  on  either  side 
are,  of  course,  reinforced  on  both  sides.  The  connection  of  the 
reinforcement  at  the  intersections  and  the  comers  of  the  bin  walls 
become  of  the  greatest  importance.  Where  possible  the  author 
prefers  to  employ  a  strong  wire  fabric  as  a  part  of  the  reinforce- 


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285 


ment  for  the  outer  walls,  nmning  this  reinforcement  horizontally 
atoiind  the  entire  building. 

Fig.  5  shows  a  common  country  elevator  of  15,000  bushels 
capacity.  The  structure  rests  upon  a  slab  or  raft  extending 
under  the  entire  building  and  connected  with  the  side  walls  so  as 
to  make  the  pit  absolutely  waterproof.      The  concrete  is  mixed 


nte 


30-0- 


EE 


\ , 


P""^ 


FIG.  6. — CONCRETE  COUNTRY  ELEVATOR. 

1  :  2  : 4  to  maximimi  density  and  to  each  bag  of  cement  is  added 
5  lb.  of  petroleum  residuum  oil  which  has  been  found  an  excel- 
lent and  cheap  method  of  making  the  walls  and  roof  impervious 
to  moistiu^e.  The  roof  and  cupola  walls  are  reinforced  with 
fabric  to  prevent  cracks  by  shrinkage. 


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Heidenreich  on  Concrete  Grain  Elevators. 


Fig.  6  shows  an  outside  wall  connection  and  the  reinforce- 
ment, illustrating  how  the  horizontal  and  hooked  members  are 
tied  to  the  vertical  rods,  to  insure  their  proper  position  until 


FIG.  6. — OUTSIDE  WALL  CONNECTION  OF  REINFORCEMENT. 

the  concrete  has  been  poured.  The  hooks  of  the  comer  rods 
(Fig.  7)  are  placed  by  springing  the  vertical  rods  until  the  comer 
rods  can  be  hooked  in  and  thereby  form  a  support  for  the  outside 
carrying  rods. 


FIG.   7. — METHOD   OF  HOOKING   CORNER  REINFORCEMENT. 

In  1911  the  com  crop  of  the  United  States  was. .  2,531,488,000  bu. 
and  of  wheat 631,388,000   " 


Total  of 3,152,786,000   " 


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Heidenreich  on  Concrete  Grain  Elevators.        287 

Most  of  this  crop  was  handled  through  farmers'  elevators, 
averaging,  say  150  cars  a  year,  or  150,000  bu.,  meaning  a  total 
of  approximately  20,000  farmers'  grain  elevators  in  the  country. 
Most  of  these  are  built  in  wood  and  will  ultimately  have  to  be 
replaced  with  concrete  construction,  which  in  turn  shows  one 
immediate  channel  for  the  use  of  Portland  cement.  The  cost 
of  a  150,000-bushel  grain  elevator  in  concrete  is  about  $5;000.00 
exclusive  of  machinery  and  millwrighting.  Considering  the 
thousands  of  wooden  elevators  rotting  away  and  burning  up  along 
our  western  trunk  and  grain  lines — ^the  almost  irreparable  loss 
to  a  town  or  community  of  farmers  when  its  elevator  bums  down, 
the  ajonual  cost  of  insurance  and  maintenance  of  these  wooden 
elevators — ^the  great  doctrine  of  conservation  brings  into  the 
limelight  the  impending  want  of  reinforced  concrete  grain 
elevators  in  every  nook  and  comer  of  the  land. 


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DISCUSSION; 


Mr.Lindau.  Mr.  Alfred  Lindau. — In  the  design  of  circular  bins  for 

exterior  pressure  of  the  space  between  the  bins,  is  account  taken 
of  the  support  that  is  afforded  by  the  adjacent  bins?  As  I  under- 
stand, the  worst  condition  is  where  the  two  opposite  spaces  would 
be  filled  with  grain  and  others  would  not  be  filled  with  grain; 
but  the  bin,  I  understand,  is  supported  on  the  other  diameter  by 
the  adjacent  bins.  Is  this  taken  into  consideration  in  the  strength 
of  the  structure,  or  merely  left  as  an  added  factor  of  safety; 
What  are  the  general  principles  that  govern  the  economy  of  grain 
storage?  Bins  are  built  high  and  you  can  build  them  wide, 
circular  or  square.  Has  an  investigation  been  made  to  show  the 
design  or  adopt  a  bin  that  would  attain  economy  for  storage 
pmposes? 

Mr.  Heidenreich.  Mr.  E.  Lee  Heidenreich. — ^Thc  location  of  the  adjacent 
bins  is  taken  into  consideration,  otherwise  we  could  use  Profes- 
sor Talbot's  formula  divided  by  16,  vxl/lQ,  in  place  of  dividing  by 
64 — ^an  empirical  factor  that  I  brought  in. 

There  are  many  items,  many  functions,  which  come  into 
play  in  the  determination  of  a  grain  elevator.  First,  the  storage 
capacity  required.  It  is  possible  to  store  grain  in  very  large 
bulk,  requiring  very  large  bins.  I  have  built  them  up  to  30,000 
and  40,000  bushel  bins  for  winter  storage.  In  other  cases  there 
are  what  we  call  pocket  bins,  carload  bins,  which  are  required 
where  certain  shippers  want  their  grain  individually,  a  practice 
quite  common.  Then  again  comes  the  floor  space.  In  a  city  the 
ground  space  is  very  expensive  and  it  is  important  to  economLee, 
and  elevators  are  built  as  high  as  possible,  as  high  as  the  soil  will 
carry  them.  If  the  soil  will  not  carry  them  they  are  put  on 
timber  piling  under  all  piers.  In  other  places,  again,  you  can 
spread  the  bins  considerably,  but,  as  a  general  rule,  to  utilize  the 
gravity  of  the  grain  in  handling  it  throughout  the  elevator  is 
considered  the  best  economy.  For  instance,  in  a  cleaning  elevator 
you  build  it  so  high  that  from  the  top  of  the  elevator  head  the 
grain  runs  first  into  the  gamer,  then  into  the  scales,  then  into  the 

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Discussion  on  Concrete  Grain  Elevators.  289 

cleaning  bin;  from  there  through  the  cleaners  and  separators  to  Mr.  Heidenreich. 

receiving  bins  and  then  into  the  loading  apparatus.    But  you  gain 

by  it,  because  the  grain  goes  by  the  gravity  from  the  top  in  one 

process  to  the  bottom  in  the  place  of  being  re-elevated,  which 

consumes  power  and  of  course  adds  to  the  cost  of  handling  of  the 

grain. 

There  are  a  great  many  other  elements  entering  into  shape  of 
grain  elevators,  but  these  are  a  few  of  the  functions  that  must  be 
considered. 

Mr.  Wm.  M.  Kinnet. — In  bms  holding  cement,  there  is  Mr.  Kinney 
often  a  sweeping  action,  similar  to  a  wave  action.  Mr.  Heidenreich 
spoke  of  the  semi-fluid  condition  of  grain,  or  an  action  like  a 
semi-fluid.  In  a  cement  bin  the  cement  will  hang  up  on  one  side 
and  all  at  once  give  way  and  sweep  clear  to  the  other  side,  across 
to  the  opposite  side  wall  of  the  tank,  and  put  a  strain  there  that 
would  have  to  be  figured  on.  I  was  wondering  whether  there  was 
anything  like  that  in  the  bins. 

Mr.  HEmENREiCH. — This  only  happens  with  wet  oats;  they  Mr.  Heidenreich. 
act  very  much  like  cement  in  bulk.  On  account  of  that  action 
instead  of  building  the  hoppers  converging  to  the  center  in  a 
cement  storage  elevator  at  South  Chicago,  they  were  built  diverg- 
ing to  the  sides,  like  over  a  peak  in  the  center  of  the  bin,  whereby 
the  hoppers  diverge  downward  toward  the  circumference,  so  that 
the  cement  in  sliding  down  the  hopper  would,  as  it  were,  spread 
itself  around  to  the  edges.  That  seemed  to  help  considerably 
against  the  wedging  proclivity  of  the  cement  at  the  top  of  the 
hopper. 

Mr.  F.  L.  Williamson. — In  connection  with  the  storage  Mr.  wiuiamson. 
of  cement  it  might  be  interesting  to  note  that  at  our  plant,  cement 
is  being  stored  in  circular  tanks,  in  interface  tanks  and  also  in 
square  tanks,  all  of  reinforced  concrete  construction.  The  storage 
tanks  are  80  ft.  deep  and  30  ft.  in  diameter.  The  interspace 
tanks,  of  course,  are  of  corresponding  size  and  three  square  tanks 
are  8  ft.  square  and  64  ft.  deep.  They  have  been  in  use  for  two 
years  and  have  proven  satisfactory.  The  strain  Mr.  Kinney 
speaks  of  has  no  doubt  been  exerted  many  times  and  with  no 
damaging  effects. 


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REPORT  OF  THE  COMMITTEE  ON  MEASURING 
CONCRETE. 

Engineers  and  contractors  for  reinforced  concrete  structures 
have  long  felt  the  need  of  some  standard  method  of  measuring 
quantities  in  contracts  for  concrete  work.  This  is  especially 
the  case  in  drawing  up  and  adjusting  unit  price  contracts.  At 
present,  although  mo^t  engineers  and  contractors  measure  and 
estimate  on  the  same  general  principles,  they  nearly  all  differ 
in  the  details  of  their  work,  with  the  result  that  disputes  occur 
and  sometimes  serious  loss  is  occasioned  or  injustice  done.  A 
feeling  exists  that  some  of  the  principles  or  fundamental  rules 
of  measurement  are  founded  on  a  wrong  basis  and  need  careful 
consideration  and  revision.  With  this  object  in  view  this  Com- 
mittee was  appointed  last  year  to  consider  the  matter  and  now 
submits  its  report. 

In  submitting  these  Proposed  Standard  Methods  the  Com- 
mittee wishes  to  call  attention  to  the  purpose  for  which  they  are 
intended  and  the  principles  by  which  they  were  guided  in  fram- 
ing them. 

The  purpose  is,  first,  to  establish  a  correct  method  for  award- 
ing unit  price  contracts  and  for  measuring  up  work  performed 
under  the  same;  second,  to  inform  concrete  contractors  and 
engineers  of  the  best  methods  of  estimating  their  work  and  work- 
ing up  unit  costs;  third,  it  the  above  two  objects  are  attained 
there  is  likely  to  be  greater  uniformity  in  published  cost  data. 

The  principles  which  have  guided  the  Committee  in  draw- 
ing up  these  rules  are  of  great  importance  and  are  as  follows: 

First, — All  work  shall' be  measured  net  as  fixed  or  placed 
in  the  building  or  structure,  and  therefore  material  cut  to  waste, 
voids,  temporary  work,  etc.,  shall  not  be  allowed  for  in  measure- 
ment but  in  price. 

Second. — In  no  case  shall  non-existent  material  be  measured 
to  pay  for  extra  labor  in  different  parts,  but  such  diflScult  or 
expensive  parts  or  extra  labor  shall  be  separately  measured 
and  described. 

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Report  of  Committee  on  Measuring  Concrete.     291 

Third, — That  all  the  chief  items  of  labor  and  material  entering 
into  the  cost  of  concrete  work  shall  be  separately  measured  and 
described  by  units  that  correctly  represent  the  labor  and  material 
involved. 

It  follows  from  the  first  and  second  of  these  principles  that  all 
work  shall  be  measured  as  it  stands,  and  that  forms  or  extra  labor 
in  placing  concrete  work  shall  not  be  allowed  for  by  doubling  or 
trebling  the  measurements  of  concrete,  and  that  laps  in  reinforce- 
ment should  be  measured. 

The  acceptance  of  the  third  principle  involves  the  recognition 
of  the  several  items  entering  into  the  cost  of  a  mass  of  concrete 
as  separate  and  distinct  operations,  viz: 

(1)  Concrete  mixing  and  placing. 

(2)  Forms. 

(3)  Reinforcement. 

(4)  Surface  finish. 

The  separation  of  forms  from  concrete  is  not  in  opposition  to 
the  first  principle  of  omitting  incidental  work,  as  forms  should  be 
considered  as  an  item  of  labor.  The  labor  of  supporting  wet 
concrete  by  means  of  forms  is  entirely  distinct  from  the  labor 
of  mixing  and  placing  concrete  and  is  done  by  different  men  at  a 
higher  rate  of  pay.  It  is  a  distinct  operation  in  the  progress  of 
the  work  and  not  a  labor  incidental  only  to  the  placing  of  the 
concrete. 

The  committee  realizes  that  the  proposed  methods  if  generally 
adopted  will  be  used  and  administered  by  inspectors,  superin- 
tendents and  foremen,  as  well  as  by  engineers,  architects  and 
contractors.  There  are  some  who  will  search  for  opportunities 
for  taking  imfair  advantages  of  the  methods  for  their  own  profit 
while  many  will  catch  the  spirit  and  use  them  fairly.  It  is,  there- 
fore, very  necessary  that  care  should  be  taken  to  provide  no  oppor- 
tunity for  fraud  or  unfair  dealing. 

In  framing  methods  of  measurement  the  Committee  has  felt 
that  it  is  not  necessary  to  give  instructions  as  to  how  to  measure, 
but  only  as  to  what  units  should  be  used  in  measuring  and  what 
items  should  be  included  or  left  out  of  such  measurements.  For 
instance,  it  is  necessary  to  say  whether  I-beams  shall  be  deducted 
or  not  deducted  from  the  mass  of  concrete  work,  but  it  is  not 


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292     Report  of  Committee  on  Measuring  Concrete. 

necessary  to  give  a  method  as  to  how  to  measure  the  irregular  thick- 
ness of  a  tunnel  lining  or  of  the  backing  to  a  masonry  wall.  The 
latter  are  matters  of  mensuration  and  outside  the  scope  of  this 
report. 

The  Committee  has  endeavored  to  keep  to  methods  of  measure- 
ment only  as  distinct  from  methods  of  cost,  and  in  general  no 
instructions  are  given  as  to  the  way  to  fix  the  price  or  cost  of  any 
item,  or  as  to  how  to  make  up  any  prices  for  work  measured  under 
these  methods.  For  instance,  the  cost  of  plant  is  added  by  some 
contractors  to  the  per  yard  cost  of  concrete  while  by  others  it 
is  taken  as  a  lump  sum  at  the  end  of  their  estimate  Nothing 
is  said  about  this  and  in  the  committee's  judgment  should  not  be. 

The  Committee  wishes  to  lay  very  special  emphasis  upon  the 
classification  of  concrete,  forms,  reinforcement  and  surface  finish 
into  separate  items.  It  is  realized  that  especially  in  the  case  of 
forms  a  radical  departure  from  the  present  method  of  measuring 
imits  is  recommended,  but  after  careful  consideration  the  Committee 
feels  convinced  that  the  present  method  of  including  forms  and 
finish  and  sometimes  steel  in  the  cubic  measurement  of  mono- 
lithic concrete  is  fundamentally  wrong  and  should  be  altered. 
A  few  instances  will  be  cited  to  make  this  point  clear. 

Supposing  a  contractor  takes  a  contract  for  a  building  with 
unit  prices  per  cubic  foot  for  concrete  in  floor,  columns  and  foun- 
dations, the  said  unit  to  include  the  cost  of  forms  and  granolithic. 
If  the  engineer  decides  to  reduce  the  thickness  of  the  floor  slab 
from  5  to  4 in.  the  contractor  has  to  put  in  just  as  much  form  work, 
but  is  paid  for  only  80  per  cent  of  the  form  work  he  estimated 
upon.  If  the  building  was  increased  from  two  stories  to  three 
stories  in  height  and  floors  were  finished  in  granolithic  he  would 
have  to  finish  twice  as  many  floors  with  granolithic  as  he  estimated. 
Or  vice  versa,  suppose  a  wall  shown  8  in.  thick  is  increased  to  12  in. 
thick,  the  owner  has  to  pay  for  50  per  cent  more  forms  and  surface 
finish  than  before,  although  the  amount  done  is  the  same.  In  a 
dispute  recently  settled  in  the  courts  a  contract  provided  for  a 
certain  price  per  cubic  yard  being  paid  for  concrete  foundations, 
this  price  covering  the  cost  of  concrete,  forms  and  steel.  In  the 
execution  of  the  work  it  was  found  necessary  to  make  the  footings 
deeper  than  shown,  but  most  of  the  steel  was  omitted.  The 
contractor  claimed  that  though  the  steel  was  omitted  his  contract 


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Report  op  Committee  on  Measubing  Concrete.     293 

price  per  yard  of  concrete  was  the  one  he  was  entitled  to  be  paid 
on  even  if  some  of  the  steel  was  left  out.  The  court  upheld  his 
view  and  he  received  judgment  accordingly. 

These  instances  are  t3rpical  of  the  gambling  nature  of  the  pres- 
ent system  of  letting  and  taking  contracts  for  concrete  at  an 
inclusive  unit  price  per  cubic  foot,  and  the  Committee  feels  con- 
fident that  if  the  methods  suggested  are  adopted  they  will  be 
of  real  value  to  the  community,  eliminating  such  uncertainties 
and  inequalities.  Very  few  contractors  in  the  present  day  like 
to  take  these  gambling  contracts. 

In  other  respects  the  Conunittee  has  endeavored  to  conform  as 
far  as  possible  to  the  general  practice  in  this  country  and  desires 
to  make  it  standard. 

Some  of  the  detailed  points  involved  in  the  methods  submitted 
will  now  be  considered. 


I.    Monolithic  Concrete. 
(a)  Concrete. 

The  rule  stating  that  concrete  in  diflferent  parts  of  the  build- 
ing or  structures  shall  be  measured  and  described  according  to 
its  accessibility  and  location  and  the  purpose  of  the  work  would 
indicate  that  there  should  be  separate  measurements  appearing 
in  the  bill  of  quantities  for: 

Concrete  in  footings. 

Concrete  in  columns. 

Concrete  in  floors,  beams  and  girders. 

Concrete  in  paving. 

Concrete  in  basement  walls. 

Concrete  in  curtain  walls  and  partitions. 
And  so  on  according  to  the  nature  of  the  work. 

Concrete  in  mass  foundations. 

Concrete  in  abutments. 

Concrete  in  arch  ribs. 

Concrete  in  spandrel  walls. 

Concrete  in  bridge  floors  and  beams. 

Concrete  in  parapet  walls  and  cornices. 
And  so  on  according  to  the  nature  of  the  work. 


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294     Repobt  op  Committee  on  Measuring  Concrete. 

In  the  event  of  any  of  these  items,  such  as  columns,  foot- 
ings, etc.,  being  of  different  mix  on  different  floors  or  places, 
these  also  would  be  measured  separately  (see  Appendix  I). 

The  matter  of  placing  bolts,  inserts,  pipes,  etc.,  in  the  con- 
crete was  considered.  It  is  not  covered  by  any  rule,  as  the  Com- 
mittee held  that  it  was  not  strictly  a  concrete  item.  The  placing 
of  such  items  should  be  taken  by  the  number  or  the  lineal  foot 
as  the  case  may  be  and  not  allowed  for  in  the  price  of  concrete 
or  forms.  The  cost  of  placing  is  part  of  the  cost  of  the  item 
itself,  and  as  such  would  come  under  the  heading  of  plumbing, 
steel  work  and  so  on. 

(6)  Forms. 

After  careful  consideration  the  Committee  feels  that  the 
square  foot  of  the  surface  supported  is  the  correct  unit  for  the 
measurement  of  forms.  In  their  judgment  the  item  which  should 
be  measured  and  paid  for  is  the  operation  of  supporting  the  wet 
concrete  imtil  it  is  set.  This  item  is  practically  an  item  of  labor 
although  material  enters  into  the  cost  of  same. 

It  is  the  practice  of  some  firms  to  estimate  forms  by  the 
amount  of  lumber  used,  but  this  is  not  a  correct  unit  of  measure, 
not  only  on  the  theoretical  ground  stated  above,  but  on  the  practi- 
cal ground  that  no  two  contractors  would  use  the  same  amoimt 
of  lumber  in  erecting  a  piece  of  form  work,  and  if  lumber  on  imit 
price  contracts  were  measured  and  paid  for  by  the  board  foot 
there  would  be  an  incentive  to  a  contractor  to  use  more  lumber 
than  was  necessary  to  do  the  work. 

It  is  necessary  to  give  a  definite  unit  which  everyone  knows 
how  to  measure.  It  is  not  possible  to  determine  beforehand 
just  how  much  lumber  will  be  used  in  any  piece  of  form  work. 
It  is  not  possible  to  accurately  measure  the  amount  of  lumber 
used  during  the  work,  and  it  is  not  possible  to  take  this  amount 
from  the  lumber  bills  because  all  lumber  bought  on  a  job  does 
not  go  into  forms,  some  of  it  going  into  temporary  buildings, 
sheeting  and  shoring  and  many  other  necessary  parts.  For 
instance,  when  the  sheet  piling  of  trenches  is  done,  the  lumber 
often  goes  into  forms,  and  of  1,000  board  feet  of  roofers  delivered, 
half  may  go  to  the  forms  and  half  to  temporary  buildings.  Fur- 
ther, much  lumber  is  used  two  and  three  times.     Other  parts 


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Report  of  Committee  on  Measuring  Concrete.     295 

are  used  but  once  only  and  some  pieces  are  sawed  off  as  waste 
and  not  used  at  all,  and  if  a  rule  were  to  be  framed  that  would 
measure  lumber,  how  should  all  these  difficulties  be  provided  for. 

Paying  for  lumber  on  a  unit  price  contract  gives  to  an  un- 
scrupulous man  an  opportunity  to  claim  a  higher  payment  from 
the  owner,  or  in  the  case  of  cost  data,  for  a  foreman  to  deceive 
his  employers  as  to  the  cost  of  the  form  work  he  is  doing.  A 
superintendent  can  put  in  twice  as  much  bracing  and  posts  as 
he  actually  needs  and  make  his  costs  look  low,  and  if  the  con- 
tractor is  paid  by  the  board  foot  he  also  would  receive  payment 
for  unnecessary  work. 

In  contrast  to  these  difficulties  the  square  foot  measure- 
ment of  form  work  does  not  alter  and  is  easily  and  quickly  meas- 
ured; and  further,  even  those  who  estimate  by  the  board  foot 
have  to  determine  the  number  of  square  feet  to  be  supported 
before  computing  the  number  of  board  feet  to  be  required  in 
the  building. 

In  the  measurement  of  iSoor  forms  the  sides  of  beams  are 
added  to  the  measurement  of  under  side  of  slab  and  beams, 
although  some  contractors  take  a  flat  measurement  of  floor  sur- 
face. The  latter  method  would  work  out  unjustly  in  the  case 
of  a  change  being  made  in  the  depth  of  the  beams,  such  change 
working  to  the  detriment  of  either  the  owner  or  the  contractor, 
while  if  the  method  that  the  Committee  recommend  is  adopted 
such  a  change  will  adjust  itself. 

Some  discussion  may  be  raised  on  the  omission  of  any  allow-, 
ance  for  angle  fillets  to  columns  and  girders,  but  the  Committee 
as  practical  concrete  men  realize  that  such  items  are  a  very  small 
part  of  the  cost  of  forms  and  it  is  not  a  usual  practice  on  the  part 
of  contractors  to  estimate  them  separately.  They  believe  that 
to  measure  angle  fillet  by  the  lineal  foot,  as  has  been  suggested, 
would  prove  a  possible  source  of  misunderstanding  in  the  carry- 
ing out  of  a  contract. 

The  separation  of  forms  to  floors,  columns,  footings,  etc., 
follows  the  lines  laid  down  for  the  separation  of  concrete  items. 

In  the  case  of  forms  to  the  concrete  walls  poured  as  backing 
to  granite  or  other  facing,  the  correct  interpretation  of  the  rules 
would  be  to  measure  forms  to  one  face  only,  the  stone  facing 
doing  the  work  of  forms  on  the  other  side. 


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296     Repobt  or  Committeb  on  Measttbing  Concbete. 

(c)  Reinforcement. 

Some  may  question  the  correctness  of  making  an  allowance 
for  laps  or  passings  in  steel  rods  or  fabric  for  reinforcement.  The 
Committee  after  careful  consideration  felt  that  these  ought  to 
be  allowed.  Laps  are  for  two  purposes,  one  as  in  beam  steel  to 
take  up  negative  moment,  and  the  other  to  provide  suflScient 
bond  to  take  up  the  tensile  strength  in  two  bars  where  one  bar 
cannot  be  obtained  long  enough  for  the  purpose.  In  the  first 
case  no  question  would  arise  as  to  measuring  the  full  length  of 
each  rod;  in  the  second,  we  think  that  as  the  specification  usually 
specifies  the  lap  to  be  a  certain  number  of  diameters,  usually 
forty  or  fifty,  there  would  be  little  difficulty  on  this  head. 

There  is,  of  course,  an  opportunity  for  unfair  dealing  by  a 
contractor  in  putting  in  steel  in  short  lengths.  A  rule  not  allow- 
ing lap  would  sometimes  work  hardship  the  other  way  if  an  in- 
spector insisted  that  steel  should  go  in  in  short  lengths  instead 
of  long,  and  then  only  pay  for  a  rod  the  net  length  of  the  build- 
ing. An  example  would  be  in  a  floor  of  a  building  laid  out  in  10  ft. 
bays  where  rods  could  be  put  in  one  length  over  one,  two  or  three 
bays  as  desired. 

The  CJommittee  feels  that  the  rule  they  have  formulated 
should  stand.  It  is  in  accordance  with  the  first  fundamental 
principle  laid  down  and  all  work  should  be  measured  net  as  fixed 
in  place.  They  believe  that  any  engineer  would  use  reasonable 
discretion  in  refusing  to  measure  laps  if  it  was  apparent  that  too 
many  had  been  made  for  an  unfair  purpose. 

III.    Structural  Cast  Concrete. 

The  use  of  structural  cast  concrete  is  growing  rapidly,  is  of 
an  entirely  different  nature  than  monolithic  concrete,  and  the 
Committee  has  endeavored  to  treat  this  part  of  the  subject  in 
a  way  similar  to  which  structural  steel  is  measured  and  estimated. 

It  is,  therefore,  not  suggested  that  forms  be  measured  sepa- 
rately, but  recommended  that  erection  should  be  separate  from 
making  and  that  the  unit  of  weight  be  the  correct  unit  for  measur- 
ing erection  rather  than  the  unit  of  volume. 

In  measuring  or  computing  erection  quantities,  it  is  recom- 
mended that  an  arbitrary  weight  of  150  lbs.  per  cu.  ft.  be  adopted 


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RePOBT  op  COMMITTEk  ON  MEASURING  CONCRETE.       297 

(similar  to  the  rule  for  steel).  This  method  will  save  the  ex- 
pense of  weighing  each  piece  and  a  good  deal  of  dispute.  This 
rule  would  not  apply  to  cinder  concrete,  for  which  another  weight 
should  be  agreed  upon. 

In  buildings  built  partly  of  cast  concrete  and  partly  of  mono- 
lithic concrete,  monolithic  concrete  would  be  measured  under  the 
rules  laid  down  for  same  and  the  cast  concrete  under  the  structural 
cast  concrete  rules. 

The  Committee  doesnot  recommend  that  grouting  be  measured. 
This  is  looked  upon  as  a  small  labor  item  incidental  to  the  erec- 
tion of  the  concrete  members  and  similar  in  character  to  riveting 
on  structural  steel  work  or  mortar  in  laying  cut  stone. 

IV.    Cast  Concrete  Trim  and  Ornamental  Work. 

Cast  concrete  trim  and  ornamental  work  is  more  nearly 
akin  to  cut  stone  work  than  to  any  other  trade.  The  Committee 
has  followed  the  custom  of  the  cut  stone  trade  and  based  the  rules 
on  stone  mason  rules,  viz:  to  measure  the  smallest  rectangular 
solid  out  of  which  a  piece  can  be  taken  for  any  piece  of  trim,  in- 
stead of  measuring  the  net  volume  of  the  finished  block. 

Surfacing  is  generally  done  in  the  mold  and  therefore  should 
not  be  separated. 

Temperature  reinforcement  is  a  very  small  part  of  the  cost 
and  for  that  reason  is  not  separated. 

Trim  serving  any  structural  purpose  such  as  lintels  with 
reinforcement  in  same  to  take  tensile  strength  should  be  classi- 
fied as  structural  cast  concrete  and  measured  accordingly. 

As  the  stone  mason's  unit  of  erection  is  the  same  as  the  unit 
by  which  he  supplies  the  stone,  the  Committee  does  not  suggest 
that  erection  be  separated  from  making. 

The  Committee  has  not  at  present  drafted  rules  covering 
plastering,  waterproofing,  concrete  blocks,  concrete  piles,  etc., 
except  in  so  far  as  they  are  covered  by  the  general  rules  governing 
surface  finish,  concrete  trim  and  structural  cast  concrete. 

Plastering  is  understood  to  be  any  surface  coating  of  cement 
or  lime  mixed  with  fine  aggregates  on  soffits  or  vertical  surfaces 
which  is  put  on  by  hand  without  the  use  of  forms. 


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298     Report  of  Committee  on  Measuring  Concrete. 

The  rules  of  structural  cast  concrete  would  apply  to  con- 
crete piles  cast  and  driven,  except  the  driving  is  usually  measured 
by  the  lineal  foot  and  not  by  the  pound,  and  the  Committee  does 
not  suggest  that  this  practice  should  be  altered. 

Respectfully  submitted  by  the  Committee  on  Measuring 
Concrete. 

Robert  A.  Cummings,  Chairman. 

L.  H.  Allen, 

Chas.  Derleth,  Jr., 

H.  H.  Fox, 

Thos.  M.  Vinton. 


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Repobt  of  Committee  on  Measuring  Concrete.     299 


Appendix  I. 

BILL  OF  QUANTITIES  FOR  A  BUILDING. 

Measured  by  Proposed  Methods. 


Concrete  1  :  2| :  5. 


CJoncrete  1:2:4. 


Concrete  1 
Cinder 

Concrete  1 
Forms. 


1J:3. 


;3:6. 


Footings 600  cu.  yds 

Basement  walls: 220  '' 

Base  to  paving 90  " 

Floors  and  beams 2,100  " 

Colunms 650  " 

Partitions  and  curtain  walls 200  '' 

WallSi  roof  and  pent  house 30  " 

Cornice  and  parapet 100  " 

Columns 110  " 


Reinforcement. 


FiU  between  screeds  (2  in.  thick) 225 

Footings l.OOOsq. 

Floor  slabs  and  beams 15,500 

C(dumns 3,500 

Curtain  walls  and  partitions 3,350 

Pent  house 900 

Basement  walls 3,000 

Parapet  and  back  of  cornice 1,200 

Face  of  cornice  36  in.  girth 400  lin. 


ft. 


ft. 


Plain  round  bars,  in- 
cluding cutting,  wir- 
ing, placing 


li  in.  dia. 
1        " 


Plain  round  bars,  in- 
cluding cutting,  wir- 
ing, placing,  but  also 
including  fabricating 
Square  twisted  bars, 
including  cutting, 
wiring  and  placing. 

1  in.  thick,  laid  integral  with  paving 

1  in.  thick,  laid  on  floors  after  concrete 

has  set 15,000 

On  cornice  and  parapet 600 

On  window  sills 1,200 

Picked  face  to  concrete  smiace 2,000 

Rubbed  face  and  cement  wash  one  coat  on  concrete  surface. . .  3,000 


Granolithic  Finish. 


i 
11 

1 

i 

I 

1x1 

ix} 


5,000  lbs, 

7,000   •' 

12,000   " 

24,500   " 

8,000   " 

17,800  " 

28,500   " 

6,000   " 

3,000   " 

8,000  " 

4,000   " 

5,000  sq. 


ft. 


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300     Report  op  Committee  on  Measuring  Concrete* 

Appendix  II. 

BILL  OF  QUANTITIES  FOR  A  BRIDGE. 
Measured  by  Proposed  Methods. 

Concrete  1:3:6.         Cyclopean  masonry  with  30  per  cent 

rock  in  foundation 2,000  cu.  yds 

Abutments 1,500       " 

Piers 1,000       " 

Abutments  (upper  part) 500       " 

Piers  (upper  part) 500       " 

Arch  ribs 1,200       " 

Columns  above  same 150       " 

Spandrel  walls  and  wing  walls 250       '' 

Bridge  floor  and  beams 600       *' 

Forms  Abutments  (below  finished  grade) 12,000  sq.  ft. 

Abutments  (above  finished  grade) 6,000       '' 

Piers  (below  finished  grade) 10,000       " 

Piers  (above  finished  grade) 8,000       " 

Arch  ribs 15,500       '* 

Columns 1,200       " 

Spandrel  walls  and  wing  walls 5,000       '' 

Bridge  floor  and  beams 12,000       " 

Parapet  wall 2,500       " 

Coping  of  same 300 lin.  ft. 

Reinforcement.  Plain  round  bars  1  Jin 30,000  lbs. 

"        "  "  1  "    50,000   " 

"    i'' 75,500   " 

"        "  "    1" 12,000   " 

"        "  "    I" 10,000   " 

Crandalled  Finish.        Piers  and  parapet 2,500 sq.  ft. 

Rubbed  Finish.  Arch  ribs  (face  and  soffits) 40,000   " 

Granolithic  Finish.        1  in.  thick  to  sidewalks  to  bridge  floor 

laid  integral  with  slab 2,000   " 

Curb  and  gutter  of  same 300  lin.  ft. 

Sidewalk.  To  approaches  with  4  in.  base  1  :  21  :  5 
and  1  in.  top  and  includes  cinder  foun- 
dation       800       •' 

Curb  and  gutter  to  last,  curb  10  in.  high, 
gutter  12  in.  wide  including  forms  and 

finish  done  in  one  operation 200       " 

Extra  for  rounded  corners  to  same  3  ft. 

girth 4 

Cast  Concrete.              Balusters  8  in.  x  8  in.  x  2  ft.  high,  includ- 
ing forms  and  steel  and  setting  in  place       50 
Coping  to  same  18  in.  x  9  in.  with  molded 
edges,  including  forms,  steel  and  finish 
and  setting  in  place 200  lin.  ft. 


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PROPOSED  STANDARD  METHODS  FOR  THE 
MEASUREMENT  OF  CONCRETE  WORK.* 

The  following  divisions  are  recognized  as  separate  and  dis- 
tinct items  in  the  construction  of  concrete  work  for  which  separate 
modes  of  measurement  are  necessary. 

I.  Monolithic  Concrete: 

(a)  Concrete. 
(6)  Forms. 

(c)  Reinforcement. 

(d)  Surface  Finish. 

II.  Sidewalks. 

III.  Structural  Cast  Concrete: 

(a)  Concrete. 

(6)  Reinforcement. 

(c)  Erection. 

IV.  Cast  Concrete  Trim  and  Ornamental  Work. 

The  following  general  rules  shall  govern  the  measurement 
of  the  above  items  (with  the  exceptions  where  specifically 
noted) : 

(a)  All  work  shall  be  measured  net  as  fixed  or  placed  in  the 
structure. 

(6)  In  no  case  shall  non-existent  material  be  measured  to 
cover  extra  labor. 

(c)  No  allowance  shall  be  made  for  waste,  voids,  or  cutting. 

I.    Monolithic  Concrete. 
(a)  Concrete. 

1.  The  unit  of  measure  for  all  concrete  shall  be  the  cubic  foot. 

2.  In  no  case  shall  the  measurement  of  concrete  be  held  to 
include  the  forms. 


*'Tbe  proposed  method*  ■ubmitted  by  the  Committee  were  disouwed.  refened  baok  to 
the  Committaa  aod  appear  here  u  amended. — Ed. 

(801) 


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302   Standard  Methods  for  Measuring  Concrete  Work. 

3.  AH  concrete  shall  be  measured  net  as  placed  or  poured  in 
the  structure. 

4.  In  no  case  shall  an  excess  measurement  of  concrete  be 
taken  to  cover  the  cost  of  forms  or  extra  labor  in  placing. 

5.  All  openings  and  voids  in  concrete  shall  be  deducted  with 
the  following  exceptions: 

(a)  No  deduction  shall  be  made  for  reinforcement,  I-beams, 
bolts,  etc.,  embedded  in  concrete  except  where  a  unit  has  a  sec- 
tional area  of  more  than  1  sq.  ft. 

(6)  No  deduction  shall  be  made  for  pipes  or  holes  in  concrete 
having  a  sectional  area  of  less  than  1  sq.  ft. 

(c)  No  deduction  shall  be  made  for  chamfered,  beveled  or 
splayed  angles  to  columns,  beams  and  other  work,  except  where 
such  chamfer,  bevel  or  splay  is  more  than  4  in.  wide  measured 
across  the  diagonal  surface. 

6.  Each  class  of  concrete  having  a  different  proportion  of 
cement,  sand  or  aggregate  shall  be  measured  and  described 
separately. 

7.  Concrete  in  the  different  members  of  a  structure  shall  be 
measured  and  described  separately  according  to  the  accessibility, 
location  or  purpose  of  the  work. 

8.  Concrete  with  large  stones  and  rocks  embedded  in  same 
(cyclopean  masonry)  shall  be  measured  as  one  item  and  described 
according  to  the  richness  of  the  mix  and  the  percentage  of  rock  in 
same. 

9.  Concrete  in  stairs  shall  be  measured  by  the  cubic  foot 
and  shall  include  surface  finish  when  the  mixture  is  the  same 
throughout. 

(6)  Forms. 

10.  The  unit  of  measure  for  form  work  shall  be  the  square 
foot  of  actual  area  of  the  surface  of  the  concrete  in  contact  with 
the  forms  or  false  work. 

11,'  Forms  shall  in  every  case  be  measured  and  described 
as  a  separate  item  and  in  no  case  shall  the  measurement  of  concrete 
be  taken  to  include  forms. 

12.  No  deduction  shall  be  made  in  measurement  of  surface 
of  concrete  supported  by  forms,  because  of  forms  being  taken 
down  and  re-used  two  or  three  times  in  the  course  of  construction. 


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Standard  Methods  for  Measuring  Concrete  Work.    303 

13.  The  unit  price  for  superficial  measurement  of  forms 
shall  be  deemed  to  include  the  cost  of  struts,  posts,  bracing, 
bolts,  wire  ties,  oiling,  cleaning,  and  repairing  forms. 

14.  No  distinction  shall  be  made  between  wood  and  metal 
forms. 

15.  Forms  to  different  parts  of  a  structure  shall  be  measured 
and  described  separately  according  to  the  position  in  the  structure, 
accessibility,  purpose  and  character  of  the  work  involved. 

16.  No  allowance  shall  be  made  for  angle  fillets  or  bevels 
to  beams,  columns,  etc.,  but  curved  moldings  shall  be  measured 
and  described  separately  as  hereinafter  provided. 

17.  No  deduction  in  measurement  of  forms  shall  be  made 
for  openings  having  an  area  of  less  than  25  sq.  ft. 

18.  No  deduction  shall  be  made  in  floor  forms  for  heads 
of  columns  of  any  shape. 

19.  No  deduction  shall  be  made  in  column  and  girder  forms 
for  ends  of  girders,  cross  beams,  etc. 

20.  No  allowance  shall  be  made  for  hand-holes  in  column 
forms  for  clearing  out  rubbish. 

21.  The  measurement  of  column  forms  shall  be  the  girth 
of  the  four  sides  or  circumference  multiplied  by  the  height  from 
the  floor  surface  to  the  under  side  of  floor  slab  above, 

22.  Forms  to  octagonal,  hexagonal  and  circular  columns  shall 
be  measured  and  described  separately  from  forms  to  square  col- 
umns. 

23.  Caps  and  bases  to  columns  and  other  ornamental  work 
shall  be  measured  by  number  and  fully  described  by  overall 
dimensions. 

24.  The  measurement  of  beam  forms  shall  be  the  net  length 
between  columns  multiplied  by  the  sum  of  the  breadth  and  twice 
the  depth  below  the  slab,  except  for  beams  at  edge  of  floor  or 
around  openings  which  shall  have  the  thickness  of  floor  added 
to  the  sum  of  the  breadth  and  twice  the  depth. 

25.  Wall  forms  shall  be  measured  for  both  sides  of  concrete 
wall. 

26.  Allowance  shall  be  made  by  number  for  pockets  left 
for   future   beams. 

27.  Moldings  in  form  work  shall  be  measured  by  the  lineal 
foot. 


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304    Standard  Methods  for  Measuring  Concrete  Work. 

28.  Forms  to  circulax  work  shall  always  be  measured  sepa- 
rately from  forms  to  straight  work. 

29.  No  measurement  or  allowance  shall  be  made  for  con- 
struction joints  in  slabs,  beams  or  arch  ribs,  to  stop  the  day's 
concreting. 

30.  Construction  joints  or  expansion  joints  to  dams  and 
other  large  masses  of  concrete  shall  be  measured  by  the  square 
foot  as   they   occur. 

31.  Forms  to  cornices  shall  be  measured  by  the  lineal  foot 
and  the  girth  stated.  (The  term  girth  shall  be  taken  to  mean 
the  total  width  of  all  curved  and  straight  surfaces  touched  by 
the  forms.)  Plain  forms  to  back  of  cornice  to  be  measured 
separately. 

32.  Forms  to  window  sills,  copings  and  similar  work  shall 
be  measured  by  the  lineal  foot. 

33.  Forms  to  the  upper  side  of  sloping  slabs  such  as  saw 
tooth  roofs  shall  be  measured  whenever  the  slope  of  such  slab 
with  the  horizontal  exceeds  an  angle  of  25  degrees. 

34.  Forms  to  the  under  side  of  stairs  shall  be  measured  by 
the  superficial  foot. 

(a)  Forms  to  the  front  edge  of  the  stairs  shall  be  measured 
by  the  lineal  foot. 

(6)  Forms  to  the  ends  of  steps  shall  be  measured  by  number. 

(c)  Reinforcement, 

35.  The  unit  of  measure  of  reinforcement  shall  be  the  weight 
in  pounds. 

36.  The  weight  shall  be  calculated  on  the  basis  of  a  square 
rod  1  in.  X  1  in.  x  12  in.,  weighing  3.4  lb. 

37.  Steel  rods  for  reinforcement  shall  be  measured  as  the 
net  weight  placed  in  the  building. 

38.  Deformed  bars  shall  be  measured  separately  from  plain. 

39.  No  allowance  shall  be  made  for  rolling  margin. 

40.  No  allowance  shall  be  made  for  cutting  or  waste. 

41.  No  allowance  shall  be  made  for  wire  ties,  spacers,  etc. 

42.  No  separation  shall  be  made  according  to  accessibility, 
location  and  purpose  of  reinforcement  except  in  special  cases. 

43.  In  measuring  reinforcement  the  rods  shall  be  measiured 
by  the  lineal  foot  as  laid.    All  laps  shall  be  allowed  for. 


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Standard  Methods  for  Measuring  Concrete  Work.  305 

44.  The  rods  of  each  dififerent  size  shall  be  measured  and 
described    separately. 

45.  Bent  bars  shall  be  measured  separately  from  straight 
bars. 

46.  Pipe  sleeves,  tumbuckles,  clamps,  threaded  ends,  nuts 
and  other  forms  of  mechanical  bond  shall  be  measured  separately 
by  number  and  size  and  allowed  for  in  addition. 

47.  Wire  cloth,  expanded  metal  and  other  steel  fabrics 
sold  in  sheets  or  rolls  shall  be  measured  and  described  by  the 
square  foot.  The  size  of  mesh  and  weight  per  square  foot  of  steel 
in  tension  shall  be  stated.  No  allowance  shall  be  made  for  waste, 
cutting,  etc.,  but  all  laps  shall  be  measured  and  allowed  for. 

(d)  Surface  Finish. 

48.  The  unit  of  measure  for  finish  of  concrete  surfaces  shall 
be  the  square  foot.  Finish  shall  always  be  measured  and  described 
separately. 

49.  No  measurement  or  allowance  shall  be  made  for  going 
over  concrete  work  after  removal  of  forms  and  patching  up  voids 
and  stone  pockets,  removing  fins,  etc. 

60.  Granolithic  finish  shall  be  measured  by  the  square  foot 
and  shall  include  all  labor  and  materials  for  the  thickness  speci- 
fied. 

51.  Finish  laid  integral  with  the  slab  shall  be  measured 
separately  from  finish  laid  after  the  slab  has  set. 

52.  No  allowance  shall  be  made  for  protection  of  finish  with 
sawdust,  sand  or  tenting. 

53.  Grooved  surfaces,  gutters,  curbing,  etc.,  shall  be  meas- 
ured separately  from  plain  granolithic  and  shall  be  measured  by 
the  square  foot  or  lineal  foot  as  the  case  may  require. 

54.  The  following  shall  be  measured  by  the  square  foot: 

Cement  wash.  (State  how  many  coats.) 

Rubbing  with  carborundum. 

Scrubbing  with  wire  brushes. 

Tooling. 

Picking. 

Plastering. 

Etc. 


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306    Standard  Methods  for  Mbasumng  Concrete  Work. 

II.    Sidewalks  and  Pavements. 

55.  Sidewalks  and  pavements  shall  be  measured  by  the 
square  foot. 

56.  The  one  measurement  shall  include  concrete,  finish,  lin- 
ing in  squares  and  cinder  or  stone  foundations. 

57.  Curbs  and  curb  and  gutter  work  shall  be  measiu'ed  by 
the  lineal  foot  and  separated  according  to  character  and  size, 
and  shall  include  foundations,  forms,  finish  and  cost  of  special 
tools  if  any. 

58.  In  measuring  curbs  the  full  height  and  width  or  thick- 
ness of  same  shall  be  taken,  but  the  measurement  of  sidewalks 
shall  also  be  taken  the  extreme  width  of  horizontal  surface. 

69.  Circular  comers  to  curbs  and  gutters  shall  be  measured 
separately  by  number,  stating  radius  and  length  measured  on 
the  curve. 

60.  Vault  lights  shall  be  measured  by  the  square  foot,  the 
measurement  to  include  glass,  forms,  steel  and  finish.  Beams 
under  vault  lights  shall  be  measured  by  the  lineal  foot.  In  measur- 
ing vault  lights  the  measurement  shall  go  at  least  4  in.  beyond 
the  outside  line  of  the  glass  in  each  direction. 

III.    Structural  Cast  Concrete. 
(a)  Concrete. 

61.  The  term  structural  cast  concrete  is  taken  to  mclude 
unit  construction  by  the  various  systems. 

62.  The  unit  of  measurement  for  structural  cast  concrete 
shall  be  the  cubic  foot,  and  shall  be  measured  net  as  provided 
for  monolithic  concrete. 

63.  The  various  members  shall  be  measured  on  the  ground 
before  erection. 

64.  No  measurement  shall  be  taken  of  forms. 

(6)  Reinforcement. 

65.  Reinforcement  shall  be  measured  separately  as  pro- 
vided in  Paragraphs  35  to  47,  inclusive. 

(c)  Erection. 

66.  The  unit  of  measure  for  the  erection  of  structural  con* 
Crete  shall  be  the  weight  of  the  finished  member  in  pounds. 


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Standard  Methods  for  Measuring  Concrete  Work.    307 

67.  In  measuring  the  erection  of  structural  cast  concrete 
having  a  crushed  stone  or  gravel  aggregate,  the  concrete  shall 
be  assumed  to  weigh  150  lb.  per  cu.  ft. 

68.  No  measurement  shall  be  taken  of  the  grouting  in 
structiu-al  cast  concrete.  It  shall  be  deemed  to  be  covered  in 
the  price  of  erection. 

IV.    Cast  Concrete  Trim  and  Ornamental  Work. 

69.  Cast  concrete  trim  shall  be  measured  by  the  cubic  foot, 
but  the  measurement  shall  be  the  smallest  rectangular  solid 
that  will  contain  the  piece  measured  and  not  its  actual  content. 

70.  No  allowance  shall  be  made  for  forms. 

71.  No  allowance  shall  be  made  for  reinforcement  in  trim 
and  ornamental  work. 

72.  No  allowance  shall  be  made  for  surface  finish  in  trim 
and  ornamental  work. 

73.  Circular  work  shall  be  measured  separately  from  other 
work. 

74.  Mitre  blocks  and  end  blocks  for  cornices,  etc.,  shall 
be  measured  separately  from  straight  molded  work. 

75.  Vases,  seats,  pedestals,  balusters  and  other  similar 
items  shall  be  measured  by  number  and  description  with  over- 
all dimensions. 


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CONCRETE  RETAINING  WALLS. 

By  J.  M.  Meade.* 

Concrete  walls  are  now  mostly  built  of  two  types,  viz.,  plain 
and  reinforced.  They  are  very  popular  for  track  elevation,  depres- 
sion and  dike  work,  especially  where  ground  is  valuable  and  they 
replace  earth  dikes  to  economize  space,  etc. 

PLAIN   MONOLITHIC   CONCRETE  RETAINING   WALLS. 

The  plain  concrete  walls  are  designed  for  what  is  known 
as  gravity  section,  being  heavy  enough  so  that  their  weight  and 
stability  will  stop  them  from  overturning.  The  best  authorities 
figure  the  width  of  base  of  such  walls  as  0.45  up  to  0.65  of  their 
height,  varying  the  width  according  to  circumstances.  Where  a 
retaining  wall  of  this  type  is  built  up  close  to  the  end  of  ties,  as 
on  an  elevated  road,  it  becomes  a  surcharged  wall.  When  designed 
as  0.45 1  have  seen  them  fail  by  pushing  over  and  would  recommend 
not  less  than  0.65  of  the  height  for  a  surcharged  wall,  finishing 
18  in.  wide  at  the  top.  The  common  practice  in  railroad  work 
of  using  arbitrary  ratios  of  width  of  base  to  height  of  walls  tends 
to  cause  a  neglect  of  the  study  of  the  proper  distribution  of  the 
pressure  on  the  foundation  and  it  seems  to  be  difficult  to  get  away 
from  such  practice.  It  is  a  well-known  fact  that  movement  from 
the  original  alignment,  due  to  unequal  settlement,  is  the  most 
common  cause  of  failures  or  defects.  The  writer  has  in  mind  some 
flagrant  cases  of  this  kind  in.  the  City  of  Chicago  that  have  caused 
:he  owners  a  very  heavy  expense.  This  question  is  one  of  great 
importance  and  each  particular  case  should  be  carefully  investi- 
gated and  studied,  so  the  amount  and  distribution  of  the  pressure 
on  the  foundation  may  be  accurately  determined. 

Many  walls  of  poor  design  have  come  to  the  attention  of  the 
writer,  there  being  entirely  overlooked,  due  to  a  lack  of  analysis 
of  the  design,  the  most  effective  section  and  minimum  amount 
of  material  for  an  economic  design. 


*  Engineer,  EaBtern  Linee,  Atchison,  Topeka  and  Santa  F6  Railway,  Topeka,  Kan. 

(308) 


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Meade  on  Concrete  Retaining  Walls. 


309 


In  constructing  retaining  walls,  it  is  of  the  greatest  importance 
that  serious  thought  be  given  to  the  matter  of  earth  filling  and 
embankments  behind  the  walls.  The  drainage  is  quite  easily 
accomplished  by  filling  or  placing  close  up  to  the  back  of  the  wall 
some  open  or  porous  material,  such  as  crushed  or  refuse  stone, 
large  size  gravel,  brick  bats,  etc. ;  cinders  will  also  do  considerable 
good.    Weep  holes  should  be  placed  in  the  wall  of  3  or  4  in.  drain 


'A 


f3 


FIG.    1. — REINFORCED  CONCRETE  TYPE  OF  RETAINING  WALL  AS  USED  IN   RAIL- 
ROAD  WORK. 

tile,  vitrified,  about  15  or  20  ft.  apart,  according  to  conditions, 
extending  the  blind  drains  to  a  point  near  the  top  of  the  wall  if 
circumstances  seem  to  warrant.  It  is  also  quite  important  in 
plain  concrete  retaining  walls,  to  use  expansion  joints  about  30  ft. 
apart,  of  the  dovetail  pattern.  If  this  is  not  done  temperature 
stresses  will  crack  the  wall.  Such  expansion  joints  are  a  good 
investment. 


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310  Meade  on  Concrete  Retaining  Walls. 

reinforced  concrete  retaining  walls. 

Reinforced  concrete  retaining  walls  consist  of  either  a  thin 
vertical  plane  attached  to  a  horizontal  base  and  well  braced  by 
counterforts  on  the  back  and  buttresses  in  front  or  they  may 
be  designed  as  cantilevers,  in  which  case  the  wall  is  connected  to 
a  wide  base  resembling  an  inverted  T. 

It  has  been  found  in  actual  practice  that  reinforced  concrete 
walls  are  more  economical  than  the  plain  monolithic  gravity  walls, 
as  the  material  in  the  latter  type  cannot  be  fully  utilized  for  the 
reason  that  the  section  must  be  made  heavy  enough  so  that  the 
dead  weight  and  size  prevent  overtmning.  On  the  other  hand, 
in  reinforced  concrete  walls  a  part  of  the  retained  material  is 
used  to  prevent  overturning  and  the  wall  only  need  be  made  strong 
enough  to  withstand  the  moments  and  shears  due  to  the  earth 
pressure.  The  wall  is  lighter  and  exerts  less  pressure  on  the  ground, 
which,  with  the  opportunity  of  extending  the  base  of  the  wall, 
often  enables  the  builder  to  use  ordinary  foundations  instead  of 
piles. 

Reinforced  walls  allow  the  use  of  a  more  scientific  design 
than  the  gravity  walls  and  have  been  known  to  be  more  reliable 
than  the  plain  concrete.  It  is  quite  common  practice  to  make  the 
base  of  these  reinforced  or  cantilever  type  of  walls  about  0.60  of 
their  height  and  then  reduce  in  size  about  as  shown  by  Fig.  1. 


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DISCUSSION. 


Mr.  Willis  Whited. — ^I  would  like  to  ask  Mr.  Meade  if  ui.  wwted, 
the  long  dike  at  Topeka  is  built  open,  exposed  to  the  action  of 
floating  ice  and,  so  far  as  he  can  judge  by  the  experience  so  far 
had,  whether  it  is  necessary  to  thicken  the  wall  to  resist  the  impact 
of  floating  ice.  We  have  some  work  in  Pennsylvania  on  some  of 
our  highways  where  it  is  necessary  to  use  a  very  long  dike  which 
will  be  exposed  almost  to  the  top  in  flood  time  and  there  would 
be  a  good  deal  of  impact  from  floating  ice  against  it. 

Mb.  John  M.  Mbadb. — ^In  a  great  many  instances  the  Mr.  Meade, 
reinforced  concrete  wall  has  proven  very  economical  in  cities. 
At  Topeka,  where  the  floods  of  1903  were  so  disastrous,  the 
river  was  diked  on  one  side  with  an  earth  dike  and  on  the  other 
side  with  a  reinforced  concrete  wall,  which  was  largely  planned 
on  account  of  the  valuable  right  of  way.  It  is  one  of  the  longest 
concrete  dikes  in  this  country,  being  about  a  mile  in  length. 
The  wall  was  finished  late  last  fall  and  of  course  we  have  not  had 
any  tests  yet.  It  is  18  in.  thick  at  the  top.  The  river  has  only 
been  up  to  above  normal  or  high  water  a  few  feet,  and  the  wall  is 
set  back  well  from  the  bank,  in  some  places  30  or  40  ft.,  so  it 
would  take  a  big  flood  to  get  above  the  banks  and  reach  this  wall. 
With  a  heavily  reinforced  wall  the  ice  would  shear  off  so  rapidly, 
going  parallel  with  the  wall,  as  to  cause  little  pounding. 

This  work  was  especially  watched  with  reference  to  its  cost 
of  construction,  etc.,  being  a  new  departure  in  dikes.  Another 
departure  was  the  use  of  Joplin  chatts.  There  have  been  some 
misgivings  as  to  the  reliability,  for  heavy  work,  of  chatts,  a  by- 
product in  the  manufacture  of  zinc.  The  chatts  can  be  had  for 
about  the  cost  of  loading,  which  is  about  15  cents  a  cu.  yd.  at 
Joplin  and  of  course  railroads  do  not  figure  the  freight.  I  had 
occasion  to  look  at  a  pier  built  over  the  Chikaskia  River  in  the 
southwestern  part  of  Kansas  on  a  line  used  jointly  by  the  Santa  F^ 
and  the  Frisco  Raiboads.  A  stone  pier  had  failed  about  eight 
years  ago  and  was  re-built  with  Joplin  chatts.  There  was  a  dam 
below  the  bridge,  so  that  the  pier  has  been  in  water  from  6  to  8  ft. 
deep  all  the  time.  I  was  very  favorably  impressed  with  the  results 
of  the  use  of  chatts  at  that  place. 

(311) 


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REINFORCED  CONCRETE  PILES. 
By  Robert  A.  Cummings.* 

It  is  well  established  that  concrete  piles  are  a  satisfactory 
substitute  for  wooden  piles  in  increasing  the  stability  of  founda- 
tions, whether  they  are  of  the  cast-and-driven  type  or  the  casi- 
in-place  type.  The  cast-and-driven  type  is  made  of  reinforced 
concrete,  molded  to  the  desired  shape  and  cured  before  being 
driven.  The  caat-dn-place  type  is  made  by  forming  a  hole  in 
the  ground  and  filling  it  with  concrete. 

The  history  of  the  cdstrand-driven  type  is  intimately  con- 
nected with  the  development  of  reinforced  concrete  and  in  the 
same  manner  has  been  embarrassed  by  patent  litigation.  In 
March,  1907,  a  final  decision  was  reached  in  the  British  High 
Courts  of  Justice  that  the  fundamental  idea  of  the  reinforced 
concrete  pile  was  covered  by  Brannon's  patent  of  1871  and  that 
subsequent  improvements  must  be  limited  to  the  details  of 
reinforcing. 

At  the  Chicago  Convention  of  this  Association  in  1909, 
the  writer  described  certain  tests  and  methods  of  reinforcing 
for  increasing  the  unit  value  of  concrete  in  compression.  It  is 
the  application  of  one  of  these  methods  and  other  practical 
improvements  that  form  the  subject  of  this  paj)er. 

It  is  nearly  ten  years  since  the  writer  began  the  design 
and  manufacture  of  concrete  piles.  During  this  period,  by  a 
process  of  elimination,  an  efficient  method  of  reinforcing  has 
been  developed,  which  is  correct  in  design  and  economical  in 
cost. 

METHOD  OF  REINFORCEMENT. 

All  piles  of  the  cast-and-driven  type  must  be  reinforced  with 
longitudinal  rods,  because  the  pile  is  hoisted  and  handled  by  a 
line  from  the  pile  driver  which  is  fastened  at  or  near  the  butt. 
Consequently,  the  pile  must  sustain  its  own  dead  weight  while 
being  raised,  as  well  as  shocks  and  impact  against  obstacles, 

*  Consulting  Engineer,  Pittsburgh,  Pa. 

(312) 


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CuMMiNos  ON  Reinforced  Concrete  Piles.  313 

before  reaching  its  position  in  the  leads  of  the  pile-driving  machine. 
.With  the  point  on  the  ground  and  the  other  end  being  elevated 
the  pile  must  act  and  be  designed  as  a  beam  supporting  its  own 
dead  weight  and  shocks.  The  limiting  proportions  of  depth  or 
thickness  of  pile  to  the  unsupported  beam  length  produces  heavy 
tensile  and  compressive  stresses,  with  considerable  deflection. 

It  has  been  observed  that  when  handling  a  pile  of  this  type, 
it  rarely  fails  in  compression  in  the  concrete,  but  cracks  are 
usually  discovered  on  the  tension  side.  These  cracks  can  be 
accounted  for  by  the  slipping  of  the  usual  longitudinal  rods  used 
in  the  concrete  while  the  pile  is  being  hoisted.  While  such  cracks 
are  not  suflSciently  serious  to  condemn  the  pile,  they  may  affect 
the  permanency  of  the  reinforcement. 

In  order  to  overcome  this  defect  all  longitudinal  rods  should 
be  anchored  at  the  ends,  those  at  the  butt  opposite  each  other 
being  bent  over  into  a  loop  and  welded  together,  while  those  at 
the  point  are  all  brought  together  and  electrically  welded  into 
one  piece.  Twisted  and  deformed  rods  are .  advantageous  for 
longitudinal  reinforcing,  as  the  allowable  bond  stress  is  higher 
than  for  plain  rods. 

The  uniform  circumferential  spacing  of  longitudinal  rods  is 
very  important,  because  any  side  of  the  pile  may  be  subjected 
to  tensile  stresses  and  whichever  side  is  in  tension  there  must 
be  sufficient  reinforcement  in  position  to  take  the  strain.  The 
circumferential  spacing  of  the  longitudinal  rods  can  be  secured 
by  means  of  a  special  spacing  device  placed  at  intervals  of  about 
5  ft.  throughout  the  length  of  the  pile. 

The  hooping  of  concrete  adds  greatly  to  its  ability  to  resist 
axial  loads.  Therefore,  longitudinal  reinforcing  should  have  a 
helical  wrapping  of  wire  throughout  the  length  of  the  pile,  the 
pitch  of  which  must  not  exceed  3  in.  This  wire  wrapping  will 
assist  in  taking  care  of  diagonal  stresses  resulting  from  the 
handling  of  the  pile. 

Practical  experience  indicates  that  the  butt  end  of  the  pile 
which  receives  the  impact  of  the  hammer  should  be  especially 
reinforced.  This  has  been  done  by  means  of  a  special  reinforce- 
ment consisting  of  a  unit  cage  of  flat  bands,  held  2  in.  on  centers 
by  a  spacing  bar  for  a  distance  of  2  ft.  In  the  plane  of  each 
band  a  flat  wire  spiral  is  fastened  to  the  cage.     The  embedment 


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314 


CxTifMiNGs  ON  Reinforced  Concrete  Piles. 


of  this  unit  cage  in  the  butt  of  the  pile  forms  a  resilient  cushion 
to  receive  the  impact  of  the  hammer.  In  no  case,  in  the  driving 
of  thousands  of  piles  with  this  cushion,  has  the  butt  itself  been 
broken. 

The  general  design  of  the  pile  is  shown  in  Fig.  1. 

METHODS  OF  DRIVING. 

Piles  of  the  aistrandrdriven  type  are  handled  and  driven  by 
means  of  an  ordinary  pile  driver.  The  ability  to  vary  the  fall 
of  the  drop  hammer  is  of  great  utility  in  overcoming  the  variable 
resistances  to  be  met  with  in  the  driving.     It  has  been  found 


r-^*~-^ 


snoops  I'x^' 


XSoffSkelSpirai 
mlpper4Ringi 


Na  5  Spirvl  mrt  S  'hfch 
FIG.    1. — ^DESIGN   OF  REINFORCED   CONCRETE   PILE. 

advisable  to  increase  the  weight  of  the  ordinary  drop  hammer 
in  ratio  of  weight  of  hammer  to  weight  of  pile  of  from  2  or  3 
to  1,  so  that  the  weight  of  the  drop  hammer  for  driving  the 
concrete  piles  will  vary  from  7000  to  12000  lb. 

Steam  hammers  are  not  as  efficient  or  desirable  for  driving 
concrete  piles  as  are  drop  hammers.  This  was  shown  last  fall 
on  a  contract  when  a  test  was  made  between  a  steam  hammer 
and  a  heavy  drop  hammer,  under  the  same  conditions,  using 
the  same  kind  and  size  of  concrete  pile.  The  heavy  drop  ham- 
mer did  not  break  a  pile,  whereas  the  steam  hammer  broke  sev- 
eral below  the  cushion.  Further,  the  steam  hammer  did  not 
drive  as  many  piles  in  a  given  time  as  did  the  drop  hammer. 


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CuMMiNGs  ON  Reinforced  Concrete  Piles.  315 

The  following  explanation  is  offered  as  it  applies  also  to 
the  driving  of  the  heavy  steel  casings  or  core  used  in  the  making 
of  the  cast-dn-place  type  of  pile:  The  limited  fisdl  (3  ft.)  and  light 
ram  (3000  lb.)  of  the  steam  hammer^  while 'delivering  twice  as 
many  blows  per  minute  as  the  drop  hammer,  loses  a  large  part 
of  its  energy  in  overcoming  the  proportionately  heavier  weight 
of  the  pile,  steel  casing  or  core. 

The  following  analytical  treatment  by  Mr.  Barton  H.  Coffey, 
of  New  York,  confirms  and  justifies  the  practice  of  the  writer 
in  using  hammers  as  heavy  as  12,000  lb.  for  driving  concrete 
piles  and  it  may  be  asserted  with  some  feeling  of  confidence  that 
if  penetration  is  to  be  the  gauge  for  measuring  the  supporting 
power  of  a  pile,  the  ratio  of  the  weight  of  the  hammer  to  the 
weight  of  the  pile  or  core  that  is  driven  must  be  taken  into  con- 
sideration. 

The  advantage  of  using  a  heavy  hammer  is  evident  from  the 
following  analysis: 

w 

Let  M  *  Mass  of  hammer=— 

9 
"    TT  =  Weight  of  hammer. 

"    X  =  Weight  or  mass  of  pile  in  per  cent  of  hammer. 

"     y  «8  Velocity  of  hammer  on  striking  pile. 

"    Vi  =  Common  velocity  of  hammer  and  pile. 

Momentum  of  hammer  =  ilf  7  (on  striking  pile. 

"  "       "        and  pile  at  common  velocity  =  Af  (i-fX)  Vi. 

These  are  equal,  provided  no  external  force  acts,  which  we 
will  assimie  for  the  present  is  the  case. 

Then  ilf  F  =  M  (1+X)  Vi]  therefore  Fi  =  fx v ^^^ 

The  energy  in  hammer  on  striking  pile  is 

»JJIfF» (6) 

The  energy  in  both  hammer  and  pile  at  common  velocity  is 
}ilf  (1 +X)  V*  which  upon  substituting  (a)  becomes  } JIf  r-r^ (c) 

The  difference  between  (6)  and  (c)  represents  the  loss  of 
kinetic  energy  in  the  system  at  point  of  common  velocity  or 
greatest  compression.     In  other  words,  the  percentage  of  the 


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316  CuMMiNGs  ON  Reinforced  Concrete  Piles. 

original  energy  of  hammer  that  has  gone  into  compressing  pile 
and  hammer^  distorting  or  crushing  them  and  into  heat,  or 
broadly,  internal  work  done  upon  each  other  by  the  striking 
bodies.  Obviously,  the  smaller  this  percentage  of  internal  work 
the  less  liability  there  is  of  crushing  or  distorting  the  pile.  To 
resume 

(c)-(6)-  }  ilf  V«  -  i  JIf  ^  -  J  ilf  F«  (l-jij^) W 

This  equals  the  internal  work. 

The  following  table  gives  internal  work  for  various  values 
of  X  in  per  cent  of  the  total  kinetic  energy  of  the  hammer. 

X  Internal  Work. 

0.25 20  per  cent 

0.50 33 

0.75 43 

1.00 50 

1.50..... 60 

2.00 67 

3.00 75 

If  the  hammer  weighs  4  tons  and  the  pile  1  ton,  there  will 
be  20  per  cent  internal  work  at  maximum  compression,  whereas 
if  the  pile  weighs  8  tons  the  internal  work  will  be  67  per  cent. 
There  is  an  external  force  acting  against  the  pile,  t.e.,  the  fric- 
tional  and  displacement  resistances  of  the  earth. 

Two  extreme  cases  may  be  assumed  limiting  all  others. 

1.  There  is  no  external  force.  There  the  internal  work 
will  be  simply  that  necessary  to  overcome  the  inertia  of  the  pile 
and  put  it  in  motion.    In  this  case  the  table  is  rigorously  accurate. 

2.  The  external  force  is  great  enough  to  prevent  any  move- 
ment of  the  pile.  In  this  case  the  entire  kinetic  energy  of  the 
hammer  goes  into  the  internal  work  and  the  relative  weights  of 
hammer  and  pile  are  immaterial. 

All  intermediate  cases  where  movement  occurs  are  a  com- 
bination of  (0  and  (2),  where  obviously  it  is  advantageous  to 
employ  a  heavy  hammer. 


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CuMMiNGS  ON  Reinforced  Concrete  Piles.  317 

MANUFACTX7RE. 

The  procedure  in  constructing  cast-andrdriven  piles  com- 
mences with  the  preparation  of  the  molding  bed.  This,  of  course, 
will  vary  with  the  site,  but  it  is  desirable  to  select  a  flat  and 
convenient  location  near  the  place  of  driving.  It  is  very  important 
that  the  bed  shall  be  stable,  so  that  settlement  due  to  the  weight 
of  the  piles  is  avoided.  Where  the  ground  is  soft  and  yielding, 
pine  stakes  2  in.  x  4  in.  x  3  ft.  long,  pointed  at  the  ends,  are 
driven  to  a  solid  bearing.  These  stakes  are  located  at  intervals 
of  about  4  ft.  in  each  direction  and  the  tops  cut  to  a  uniform 
level.  Then,  4  x  4  in.  pine  sills  are  toe-nailed  to  the  top  of  the 
stakes  in  longitudinal  rows  about  4  ft.  on  centers.  Upon  these 
sills  a  2-in.  solid  wooden  floor  is  placed,  which  forms  the  molding 
bed.  It  is  desirable  that  this  bed  shall  be  uniformly  level  to 
receive  the  forms  for  the  piles. 

The  forms  are  made  of  two  pieces  of  2  x  8-in.  dressed  pine, 
battened  together  and  placed  on  edge  to  form  the  sides  of  the 
pile.  The  bevels  or  angles  for  tapered  or  octagonal  piles  are 
made  by  placing  loose  pieces  of  bevelled  wooden  strips  at  each 
comer  of  the  form.  The  reinforcement  is  delivered  on  the  work 
in  factory-made-units,  so  that  it  can  be  placed  in  the  forms  at 
once.  When  a  reinforcing  unit  is  suspended  and  centered  in 
position,  the  concrete  of  a  wet  consistency  is  deposited  and  care- 
fully puddled.  As  soon  as  the  concrete  of  the  pile  has  solidified, 
the  forms  are  stripped  and  used  for  making  other  piles.  The 
number  of  forms  required  will  vary  with  the  quantity  of  piles  to 
be  made  and  the  prospective  salvage  in  the  lumber. 

The  curing  of  concrete  in  the  normal  manner  delays  the 
driving  of  the  piles  for  a  period  of  not  less  than  3  weeks,  although 
a  greater  length  of  time  is  desirable,  especially  in  cool  and  damp 
weather.  Therefore,  unless  a  stock  of  cured  piles  is  always  on 
hand,  it  frequently  occurs  that  this  type  of  pile  cannot  be  used 
at  all  and  resort  is  had  to  the  use  of  the  cast-dn-place  type.  This 
practice  is  open  to  question  on  account  of  the  inability  of  plain 
concrete  to  resist  even  moderate  tension.  In  fact,  it  is  almost 
axiomatic  that  all  concrete  piles  must  be  reinforced.  Every 
concrete  pile  is  subjected  to  strains  that  induce  very  serious 
tensile  stresses  in  the  pile.  Such  stresses  may  result  from  super- 
imposed loads  or  a  lateral  strain  from  the  soil.     Further,  the 


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318 


CuMMiNGS  ON  Reinforced  Concrete  Piles. 


making  and  storing  of  concrete  piles  for  use  at  any  time  necessi- 
tates a  large  financial  investment. 

In  order  to  avoid  the  above-mentioned  objections,  the  writer 
has  adopted  the  method  of  steam  curing  of  cast-and-driven  piles. 
This  enables  such  piles  to  be  made  and  driven  within  3  or  4  days 
and  places  the  speed  of  driving  on  the  same  basis  as  that  of  the 
cast-in-place  type. 

The  means  used  for  steam  curing  will  vary  with  circum- 
stances, location  of  the  work,  speed  required  for  delivery  of  the 
piles,  the  number  needed,  etc.  During  the  past  winter  the 
writer  has  used  concrete  piles  made  and  driven  within  10  days, 
and,  as  a  result  of  this  experience,  confidently  recommends  that 
such  piles  can  be  made,  cured  and  driven  immediately. 

On  the  work  with  which  the  writer  was  connected,  the  piles 


* — ^*^^..> 


PJl^^p^^  ^^-^^^^0^^ 


III 


h  -"iJ'-i?'"- - 


_J  0  J  a  D 


\s>'^  '2>  J  •: 


EN^Nt«4 


FIG.   2. — SHED   FOR  STEAM-CURING  PILES. 


were  allowed  to  set  in  a  normal  manner  for  5  or  6  days — and 
were  then  gently  hoisted^ from**^ the  molding  bed  by*a  derrick, 
using  an  equalizing  spreader  and  bridle,  the  chains  of  the  bridle 
being  fastened  so  that  the  pile  was  balanced.  They  were  then 
placed  in  stacks  of  25  or  30  and  separated  from  one  another  by 
wooden  blocks,  particular  attention  being  given  to  securing  a 
solid  bearing  for  each  pile. 

A  light  wooden  shed,  practically  steam  tight,  was  built 
entirely  around  the  stack  of  piles.  Fig.  2.  The  steam  was  con- 
ducted direct  from  a  boiler  through  a  1-in.  pipe  to  3  branch 
openings  inside  the  shed.  The  steam  pipe  valve  was  opened  and 
the  piles  were  exposed  to  live  steam  for  2  or  3  days,  when  they 
were  found  to  be  ready  for  driving.  On  being  first  exposed  to 
steam,  the  moisture  condensed  on  the  surface  of  the  piles  and 
remained  until  absorbed  by  the  concrete  when  the  temperature  of 


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CUMMINGS  ON  ReINFOBCED  CONCRETE  PiLES.  319 

the  steam  was  reached.  This  steam  treatment  should  be  distin- 
guished from  heat  applied  indirectly  or  baking,  in  accelerating 
the  set  and  hardening  the  concrete.  The  writer  sees  no  reason 
why  boiling  water  should  not  be  used  for  the  same  purpose  if 
the  conditions  are  favorable  for  adopting  this  method.  Pre- 
caution should  be  exercised  in  making  sure  that  the  concrete 
has  solidified  and  that  it  has  received  its  initial  set,  before  expo- 
sure to  steam  treatment. 

The  prospective  field  opened  up  by  the  steam  treatment 
for  the  rapid  curing  of  concrete  seems  to  the  writer  to  solve  the 
diflBculty  incidental  to  the  present  methods  of  procedure  in  the 
construction  of  all  classes  of  concrete  structures. 

Attention  is  directed  to  the  publication  of  the  tests  of  the 
Structural  Materials  Laboratory  of  the  United  States  Geological 
Survey,  wherein  it  is  conclusively  shown  "that  a  compressive 
strength  considerably  (in  some  cases  over  100  per  cent)  in  excess 
of  that  obtained  normally  after  ageing  for  six  months,  may  be 
obtained  in  two  days  by  using  steam  pressure  for  ciu*ing  mortar.'* 

Practicing  engineers  will  have  little  difficulty  in  modifying 
the  writer's  methods  and  using  improved  schemes  for  quick  cur- 
ing of  the  piles  with  steam;  and  in  this  connection  it  may  be  of 
interest  to  state  that  the  writer  has  already  under  way  the  con- 
struction of  steel  molds  and  appliances  for  the  steam  treatment 
of  concrete  piles. 

A  list  of  references  on  Concrete  Piles  to  1908  is  given  in  the 
appendix. 


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APPENDIX. 
L18T  OF  REFERENCES  ON   CONCRETE  PILES. 

Concrete  Piles  for  Sandy  Ground.  Engineering  News,  v.  49,  p.  275. 
(March  26,  1903.)  (Description  of  the  Raymond  system  of  sinking  piles 
with  water  jet.     Illustrated.)     (1  column.) 

A  Concrete-Steel  Pile  Foundation.  Engineering  News,  v.  49,  p.  173. 
(February  19,  1903.)  (Description  of  piles  used  for  the  Court  House, 
Berlin,  Germany.     Driven  by  steam  hammers.)     (1  column.) 

Concrete  Pile  Foundations,  Carnegie  Public  Library,  Aurora,  III. 
Engineering  News,  v.  48,  p.  495.  (December  11,  1902.)  (Description 
of  the  Raymond  method  of  using  steel  core  for  making  holes  for  concrete 
piles.    Illustrated.)     (§  column.) 

A  New  System  op  Concrete  Pile  Construction.  Engineering  News,  v. 
45,  p.  450.  (June  20,  1901.)  (Description  of  the  trial  of  the  Raymond 
steel  core  system,  made  at  Chicago,  May  16,  1901.  Illustrated.)  (1 
column.) 

Concrete  Pile  Foundations.  Engineering  News,  v.  46,  p.  75.  (August  1, 
1903.)  (Description  of  the  foundations  of  the  nine-story  apartment  house 
built  for  W.  J.  Bryson,  Lake  Avenue,  Chicago.  Holes  bored  by  water- 
jet  system  before  Raymond  steel  core  was  dropped.  Material  largely 
sand  and  quicksand.)     (|  column.) 

The  Hennebique  System  of  Armored  Concrete  Construction.  By 
Leopold  Mensch.  Journal  AssodcUion  of  Engineering  Societies,  v.  29, 
p.  108.  (September,  1902.)  (Contains  three  pages  on  concrete-steel 
piles.) 

Abstract  of  same.  Concrete-Steel  Piles  of  the  Hennebique  System. 
Engineering  Record,  v.  46,  p.  618.     (December  27,  1902.) 

Construction  in  Concrete  and  Reinforced  Concrete.  By  F.  C.  Marsh, 
1902.  Minutes  of  Proceedings  of  the  Institution  of  Civil  Engineers, 
V.  149,  p.  297.  (Gives  a  short  description  of  piles  made  after  the  Henne- 
bique System.) 

Neuere  Bauwesen  und  Bauwerke  in  Beton  und  Eisen,  nach  dem  Stands 
bei  der  Pariser  Weltausstellunq  1900.  Fritz  v.  Emperger,  Zeit- 
sckrifl  des  Oeslerreichischen  IngenieW'  und  Architekten-Vereines,  53. 
Jahrgang,  pp.  713  and  765.  (October  25  and  November  15,  1901.) 
(General  description  of  concrete  piles  and  their  use.)  (Illustrated.  7 
pages.) 

Abstract  of  same.  Concrete-Steel  Piles  and  their  Driving.  Engineering 
Record,  v.  46,  p.  560.  (December  13,  1902.)  (Gives  extracts  from  Mr. 
C.  F.  Marsh's  paper  read  before  the  Institution  of  Civil  Engineers  and 
from  Mr.  F.  Von  Emperger's  description  of  a  pile  driver  from  the  Zeit- 
schrift  des  Oeslerreichischen  Ingenieur-  und  Architekten  Vereines,  Novem- 
ber 7,  1902.)     (2  columns.) 

(320) 


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CuMMiNGS  ON  Reinforced  Concrete  Piles.  321' 

Concrete  Piles.  Railroad  GazeUe,  v.  34,  p.  645.  (August  15, 1902.)  (De- 
scription of  the  Raymond  System  with  illustrations  from  the  J.  I.  Case 
Plow  Works,  Racine,  Wis.)     (1  column.) 

The  Raymond  Concrete  Piles.  Cement  and  Engineering  News,  v.  13,  p. 
22.  (August,  1902.)  (Illustrated  description  of  the  Raymond  System.) 
(1  page.) 

Concrete  Pile  Foundations  op  the  Hallenbeck  Building,  New  York. 
Engineering  Record,  v.  47,  p.  377.  (April  11,  1903.)  (Piles  sunk  by 
means  of  water  jet.    Material,  gravel  and  sand.     Illustrated.)   (1  page.) 

QUAIMAUERN   UND   FuTTERMAUERN   AUB   BeTON   UND   EiSEN    (SySTEM   HeN- 

nebique).     Zeitschrift  des  Oesterreichischen  Ingenieur-  und  Architekten" 

Vereines,  53.  Jahrgang,  p.  539.     (August  9,  1900.)     (Short  descriptions 

of  quay  walls  in  Southampton,  Paris  and  Nantes.)    (Illustrated.  H  pages.) 
Ueber  Beton-Eisen-Piloten.     Zeilachrift  des  Oesterreichischen  Ingenieur- 

und  ArchUekien^Vereines,  54.  Jahrgang,  p.  746.      (November  7,  1902.) 

(Illustrated.    2  pages.) 
Bbtoneisen-Ppahlrost   vom   Neubau   des  Amtsgerichtes-Weddinq   in 

Berlin.    Deutsche  Bauzeitung,  36.  Jahrgang,  p.  582.    (November,  1902.) 

(1  page.) 
Pfahlrobtkonbtruktionen   in   Beton-Eisen.      Deutsche  Bauzeitung,  36. 

Jahrgang,  p.  411.     (August,  1901.)     (Short  description  of  use  of  concrete 

piles  according  to  Hennebique  system  for  a  building  for  Holland-American 

line  in  Rotterdam.)     (i  column.) 
Beton-Pfbiler    der    SANGAMON-FLUSS-BRtJcKE.      Thonindustrie    Zeitung, 

26.  Jahrgang,  1.  Halbjahr,  p.  83.     (January  17,  1901.)     (Description  of 

the  use  of  concrete  piles  for  the  St.  Louis,  Peoria  and  Northern  Railroad 

Bridge  over  the  Sangamon  River.)     (f  column.) 

StaHL-BeTON-PfEILER  Fto  DIE  CLYBOURN-PLACE-BRtJCKE  IN  CHICAGO,  IlL. 

Thoninditsirie-ZeUung,  25.  Jahrgang,  1.  Halbjahr,  p.  631.  (April,  1901.) 
(Short  description  of  steel-concrete  piles  for  a  drawbridge  over  Chicago 
River.)     (i  column.) 

EiNRAMMEN  VON  Betonpfahlen.  ThonindiLstrie  Zeitung,  27.  Jahrgang,  1. 
Halbjahr,  p.  296.  (February  21,  1903.)  (Short  description  of  method 
of  driving  concrete  piles.)     (Illustrated.)     (i  column.) 

Ueber  Betonpfahle.  Thonindustrie  Zeitung,  27.  Jahrgang,  1.  Halbjahr, 
p.  1106.  (June  13,  1903.)  (Short  description  of  construction  and 
method  of  driving  concrete  piles.)     (Illustrated.)     (§  column.) 

Recent  Developments  in  Pneumatic  Foundations  for  Buildings.  By 
D.  A.  Usina,  Associate  American  Society  Civil  Engineers.  Proceedings 
American  Society  of  CivU  Engineers,  v.  34,  p.  220.  (March,  1908.) 
(Contains  two  pages  on  the  comparison  of  concrete  piles  and  caissons  for 
foundations  of  buildings.) 

Foundations;  an  Informal  Discussion  at  the  Annual  Convention, 
July  10,  1907.  Proceedings  American  Society  Civil  Engineers,  v.  33,  p. 
812,  816.     (September,  1907.)     (Contains  some  data  on  concrete  piles.) 

CoNCBBTE  and  Concrete-Steel.  Transactions  American  Society  CivU 
Engineers,  v.  54,  Pt.  E.,  pp.  436,  461,  469,  548,  615.     (International 


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322  CuMMiNGs  ON  Reinforced  Concrete  Piles. 

Engineering  Congress,  St.  Louis,  1904.)  (Very  short  references  to 
concrete  piles.) 

Cyundrical  Foundations  for  a  Quay  Wall  in  the  Harbor  of  Dblfzyl. 
By  W.  F.  Druyvesteyn.  Transactions  American  Society  Civil  Engi- 
neers^ V.  54,  Ft.  E.  (International  Engineering  Ck)ngres8y  St.  Louis, 
1904.)    (Contains  1  page  on  concrete  piles.) 

Use  of  Reinforced  Concrete  in  Buildings.  By  Frank  C.  Schmitz. 
Proceedings  Brooklyn  Engineers^  Club,  1906,  p.  67.  Brooklyn,  N.  Y. 
1907 .  (Contains  a  short  table  comparing  the  price  of  wooden  and  concrete 
piles.) 

Driving  Concrete  Piles  Below  the  Battery  Tunnel,  New  York. 
Engineering  Record,  v.  65,  p.  678.  (June  8,  1907.)  (The  construction 
consists  of  a  series  of  transverse  pile  bents  at  irregular  intervaLs  of  about 
50  feet  supporting  the  undersides  of  the  tubes  for  two  lengths  of  about 
600  feet  each.  In  each  bent  there  are  two  reinforced  concrete  piles  20 
inches  in  diameter  and  about  7  feet  apart  on  centers.) 

Grade  Correction  and  File  Foundations  in  the  East  River  Tunnel 
OP  THE  New  York  Rapid  Transit  Subway.  Engineering  News,  v.  57, 
p.  718.  (June  27,  1907.)  (An  illustrated  description  of  the  construction 
of  the  reinforced  concrete  piles.) 

Concrete  Pile  Foundations  for  a  Tower  7(X)  Feet  High.  Engineering 
Record,  v.  55,  p.  531.  (April  27,  1900.)  (The  piles  are  of  the  Raymond 
concrete  type  and  are  made  in  the  standard  manner  by  ^t  driving  with 
a  solid  steel  core  a  thin  conical  steel  shell,  which  excludes  water  and  sand 
and  is  filled  with  concrete  after  the  core  is  withdrawn.) 

Steamship  Terminal  with  Concrete  Pile  Piers  at  Brunswick,  Ga., 
Atlantic  and  Birmingham  Railway.  Engineering  News,  v.  56,  p.  654. 
(December  20,  1906.)  (Gives  specifications  for  concrete  piles,  illustra- 
tions and  method  of  construction.) 

Cement  Piers.  Scientific  American  Supplement,  v.  63,  p.  26241.  (May  25, 
1907.)  (The  cement  cylinders  for  use  in  piers  at  San  Francisco  are  made 
of  three  wooden  piles  enclosed  in  reinforced  concrete.) 

Improved  System  of  Concrete  Piling.  Journal  of  tke  Franklin  Institute, 
v.  160,  p.  455.  (December,  1905.)  (A  report  of  a  committee  on  the 
merits  of  the  concrete  pile  invented  by  Frank  Shuman,  illustrated.) 

The  Simplex  System  op  Concrete  Piling.  By  Constantine  Shuman. 
Proceedings  Engineers*  Club  of  Philadelphia,  v.  22,  p.  347.  (October, 
1905.)     (lUustrated.) 

Concrete  Piles,  Description  of  the  Methods  of  Manufacture  and 
Usages  of  the  Two  Leading  Types  op  Concrete  Piles  which  are 
Replacing  the  Wooden  Products.  By  David  Lay.  Cement  Age, 
V.  2,  p.  626.    (February,  1906.) 

Reconstruction  of  the  Atlantic  City  ** Steel  Pier"  in  Reinforced 
Concrete.  Engineering  News,  v.  56,  p.  90.  (July  26,  1906.)  (The 
reinforced  concrete  piles  were  molded  on  small  pile  platforms  adjacent 
to  the  location  of  the  piles  in  the  piers;  after  hardening  the  piles  were 
lifted  from  the  platforms,  set  in  position  and  sunk  into  the  sand  by 
means  of  a  water  jet,  having  a  pressure  of  65  lbs.  per  sq.  in.) 


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CuMMiNGs  ON  Reinforced  Concrete  Piles.  323 

Cost  of  Making  and  Placing  Reinforced  Concrete  Piles  at  Atlantic 

City,  N.  J.     Engineering  News,  v.  56,  p.  252.     (September  6,  1906.) 
The  Manufacture  and  Use  of  Concrete  Piles.     By  Henry  Longcope. 

Proceedings  National  Association  of  Cement  Users,  v.  2,  p.  277.     (1906.) 
Abstracts  of  same.     Scientific  American  Supplement,  v.  61,  p.  25375.     (May 

12,  1906.)     Municipal  Engineering,  v.  30,  p.  106.     (February,  1906.) 
Reinforced  Concrete  Pile  Foundation  for  the  Lattemann  Building, 

Brooklyn,  N.  Y.     Engineering  News,  v.  54,  p.  594.      (December  7, 

1905.)     (The  piles  used  were  of  the  corrugated  form  invented  by  Frank 

B.  Gilbreth.) 
The  Making  and  Driving  of  Corrugated  Concrete  Piles.     By  Frank 

B.  Gilbreth.     Association  of  American  Portland  Cement  Manufacturers, 

Bulletin  No.  7.     (1906.)     (Illustrated.) 
L'Emploi  des  Pieux  en  B£ton  pour  les  Fondations.     Le  Genie  Civil,  v. 

49,  p.  104.     (June  16,  1906.)      (An  illustrated  description  of  different. 

types  of  concrete  piles.) 
Translation  of  same  by  George  L.  Fowler.     The  Use  op  Concrete  Piles. 

RaUroad  Ga^tU,  v.  41,  p.  238.     (September  21,  1906.) 
Appontement  M£tallique  de  Lome  (Afrique  occidentale).     Le  Genie 

Civil,  v.  47,  p.  178.     (July  15,  1905.)     (Contains  a  description  of  the 

concrete  piles.) 
Corrugated  Concrete  Foundation  Piles.    Engineering  Record,  v.  52,  p. 

548.      (November  11,  1905.)     (Describes  the  method  of  constructing 

the  foundations  for  the  Lattemann  Building.  Brooklyn.) 
Building  and  Machinery  Foundations  in  Quicksand.    Engineering  Record, 

V.  53,  p.  248.      (March  3,  1906.)      (For  the  Knickerbocker  Building, 

New  York  City,  the  foundations  of  the  column  and  wall  piers  consist 

of  clusters  of  tubular  steel  piles  12  in.  in  diameter  and  {  in.  thick  sunk  to 

bed  rock  and  filled  with  concrete.) 
Concrete  Piling.     Scientific  American,  v.  90,  p.  248.     (March  26,  1904.) 
Die  GrI^ndung  des  Amtsgerichtsgebaudes  auf  dem  Wedding  in  Berlin 

MIT  BetoneisenpfXhlen.     By  Hertel.     Beton  und  Eisen,  v.  2,  p.  246. 

(October,  1903.) 
Reinforced  Concrete  Piling.     By  A.  R.  Galbraith.     Proceedings,  Incor- 
porated AssocicUion  of  Municipal  and  County  Engineers,  v.  31,  p.  356. 

(1904-5.)     Spon  &  Chamberlain,  123  Liberty  Street,  New  York. 
Abstract  of  same.     European  Reinforced  Concrete  Piles.     Engineering 

Record,  v.  52,  p.  99.     (July  22,  1905.) 
Concrete  Piles  at  the  United  States  Naval  Academy.     By  Walter  R. 

Harper.     Engineering  Record,  v.  51,  p.  277.     (March  4,  1905.)     (Gives 

the  comparative  cost  of  wood  and  concrete  piles;   test  of  concrete  pile 

and  methods  of  construction.) 
The  Strength  of  Pile  and  Concrete  Foundations.     Engineering  Record, 

V.  50,  p.  358.     (September  24,  1904.)     (Results  of  experiments  made  to 

determine  the  adhesion  of  timber  piles  to  concrete,  when  imbedded  in 

that  material.) 


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324  CuMMiNGS  ON  Reinforced  Concrete  Piles. 

Concrete  Pile  J'oundations  at  Washington  Barracks,  D.  C.  By  Captain 
John  Stephen  Sewell.  Engineering  Record,  v.  50,  p.  360.  (September 
24,  1904.)     (2  pages.) 

Reinforced  Concrete  Piles  with  Enlarged  Footings  for  Underpinning 
A  Building.  By  J.  Albert  Holmes.  Engineering  Record,  v.  51,  p.  567. 
(June  16,  1904.)  (Describes  the  construction  of  piles  for  the  foundation 
of  a  building  in  Boston,  Mass.) 

Des  Applications  du  Ciment  Arm£.  By  G.  Liebeaux,  Reime  Generate 
des  Clieynins  de  Fer,  v.  24,  Pt.  2,  p.  525.  (December,  1901.)  (Contains 
illustrations  of  concrete  piles  for  foundations.) 

Notes  on  European  Reinforced  Concrete  Structure.  Engineering 
Record,  v.  51,  p.  38.  (January  14,  1905.)  (Contains  one  column  on 
ferro-concrete  piles.) 

Reinforced  Concrete.  (Pt.  162,  375.)  By  Albert  W.  Buel  and  Charles 
S.  Hill.  Ed.  2,  N.  Y.,  1906.  Engineering  News  Publishing  Company, 
220  Broadway.     $5  net.     (Contains  data  on  concrete  piles.) 

Abstract  of  same.  The  Construction  and  Use  of  Concrete  Steel  Piles 
IN  Foundation  Work.  Engineering  News,  v.  51,  p.  233.  (March  10, 
1904.) 

Concrete-Steel  Piles.  Cement,  v.  4,  p.  16.  (March,  1903.)  (A  descrip- 
tion of  heavy  pile  drivers  designed  for  driving  concrete-steel  piles.) 

A  Treatise  on  Concrete  Plain  and  Reinforced.  (P.  477.)  By  Fred- 
erick W.  Taylor  and  Sanford  E.  Thompson,  Associate  Members,  American 
Society  Civil  Engineers,  N.  Y.,  1905.  John  Wiley  &  Sons,  43  East 
Nineteenth  Street.     $5. 

Concrete  and  Reinforced  Concrete  Construction.  (P.  428.)  By 
Homer  A.  Reid,  Associate  Member,  American  Society  Civil  Engineers, 
N.  Y.  1907.  Myron  C.  Clark  Publishing  Company,  13  Park  Row. 
$5  net.     (Gives  data  on  concrete  piles.) 

Reinforced  Concrete.  (Pp.  41,  181,  200,  449.)  By  Charles  F.  Marsh, 
Member  American  Society  Civil  Engineers,  and  William  Dunn.  Ed.  3, 
London,  1906.  Archibald  Constable  &  Co.,  Ltd.,  16  James  Street, 
Haymarket.    $7  net.     (Very  short  references.) 

Cement  and  Concrete.  (P.  485.)  By  Louis  Carlton  Sabin,  Member  Amer- 
ican Society  Civil  Engineers.  Ed.  2,  New  York,  1907.  McGraw 
Publishing  Company,  239  West  Thirty-ninth  Street.  $5.  (Contains 
2  pages  on  concrete  piles.) 

Concrete  Steel.  (P.  169.)  By  W.  Noble  Twelvetrees,  New  York,  1905. 
Whittaker  &  Co.,  64  Fifth  Avenue.  $1.90.  (Contains  10  pages  on  con- 
crete-steel piles.) 

Reinforced  Concrete  Piles;  Their  Making  and  Driving.  Cement, 
V.  4,  p.  331.     (November,  1903.) 

A  New  System  op  Concrete  Piles.  By  W.  P.  Anderson,  Engineering  Record, 
V.  50,  p.  494.  (October  22,  1904.)  (Piling  for  the  Dittman  factory 
building,  Cincinnati,  Ohio.) 

Concrete  Piles  for  Building  Foundations.  Engineering  Record,  v.  49, 
p.  596.     (May  7,  1904.)     (2  columns.) 


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CiJMMiNGs  ON  Reinforced  Concrete  Piles.  325 

A  Practical  Treatise  on  Foundations.  (Pp.  467,  477.)  By  W.  M. 
Patten,  Ed.  2,  New  York,  1906.  John  Wiley  &  Sons.  $5.  (Contains 
information  on  concrete  piles.) 

EiNE    NEUERB     KaIMAUER    MIT    ElSENBETON-PFAHLGRt^NDUNG.       ZeUschrifi 

fUr  Baurvesen,  v.  57,  p.  550.  (Pt.  10-12,  1907.)  (On  the  reinforced 
concrete  piles  for  the  foundation  of  a  new  quay  wall  at  Dusseldorf.) 
Methods  and  Cost  of  Driving  Raymond  Concrete  Piles  for  a  Building 
Foundation.  Engineering-CoTitracting.  (February  13,  1907.)  (Gives 
figures  of  cost  computed  from  records  obtained  in  constructing  the  pile 
foundations  for  a  building  in  Salem,  Mass.) 

Kt^NSTLICHE  BeFESTIGUNG  DES  BaUBODENS  MITTEL8T  SCHWEBENDER  PILO- 
TAGE. By  Ottokar  Stern.  Beton  und  Eisen.  (January,  1907.)  (Calcu- 
lations and  dimensions  for  concrete  piling.) 

Concrete  Piles.  By  Charles  R.  Gow.  Journal  Associated  Engineering 
Society.    (October,  1907.)     (Illustrated.) 

The  Simplex  System  of  Concrete  Piling.  By  Thomas  MacKeller.  Jour- 
nal  Associated  Engineering  Society.     (October,  1907.) 

PiLOTis  "Simplex."    Le  Ciment.     (December,  1907.)     (Illustrated.) 

Concrete  Piles — Forms,  Advantages  and  Cost  as  Compared  with 
Wooden  Piles.  By  C.  W.  Gaylord.  Proceedings,  v.  5,  1909.  National 
Association  of  Cement  Users.     (21  pages.     Illustrated.) 


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THE  HANDLING  OF  CONCRETE  IN  THE  CONSTRUC- 
TION  OF  THE  PANAMA  CANAL. 

By  S.  B.  Williamson.* 

The  estimated  amount  of  concrete  that  will  be  used  in  the 
construction  of  the  Panama  Canal  aggregates  5,416,645  cu.  yd.  and 
is  distributed  as  indicated  in  Table  I. 

Table  I. — Status  op  Concrete  Work  on  the  Panama  Canal  on 
January  1,  1912. 


Location. 


Terminal  Docks  at  Cristobal 

Gatun  Spillway  Dam 

Gatun  Locks 

Culebra  Cut:  Revetment 

Pedro  Miguel  Ix>ck8 

Miraflores  Locks 

Miraflores  Spillway  Dam 

Terminal  Docks  at  Balboa 

Municipal     Roservoirs.     Dams,     Power     HoufM>, 
Bridges,  etc 

Totol I 


Amounts  in  Cubic  Yards. 

Placed. 

To  be  Placed. 

Total. 

500 

167.500 

1.761.345 

786."696 
671.860 

'6."535 

22.000 

51.800 
57.580 
238.895 
400.000 
111.993 
840,876 
75,000 
330.065 

62.300 

225.080 

2.000.240 

400.000 

892.689 

1.412.736 

75.000 

336.600 

22.000 

3.310.436 

2.106.209 

6.416.645 

While,  no  doubt,  it  is  generally  known  that  concrete  plays  a 
leading  part  in  the  building  of  the  Canal,  a  summary  of  the 
quantities  emphasizes  its  importance,  which  becomes  still  more 
significant  when  one  realizes  that  the  estimated  cost  of  the  con- 
crete structures  represents  23  per  cent  of  the  entire  estimate  for 
construction  and  engineering  and  that,  had  it  been  necessary  to 
adopt  stone  masonry,  the  cost  of  these  structures  would  have 
narrowly  escaped  a  prohibitive  figure,  as  there  is  no  building  stone 
within  a  reasonable  distance  from  the  Canal  Zone.  It  does  not 
seem  out  of  the  way,  therefore,  to  advance  the  claim  that  the 
lock  type  of  canal,  now  under  construction,  and  acknowledged 
to  be  the  most  preferable  by  all  engineers  who  have  given  the 
subject  careful  consideration,  became  feasible  largely  through  the 
use  of  concrete. 


*  Engineer,  Pacific  Division.  Panama. 


(326) 


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Williamson  on  Handling  Concrete  at  Panama.      327 

The  locks  comprise  a  large  proportion  of  the  total  quantity 
of  masonry  and  in  order  to  place  the  amount  of  concrete  involved, 
economically  and  at  a  rate  to  accomplish  the  work  within  the 
allotted  time,  it  was  necessary  to  devise  especial  and  unusual 
handling  appliances;  and  it  is  the  purpose  of  the  writer  to  describe 
the  plants  and  methods  adopted. 

GATUN   LOCKS. 

General  Description. — ^At  Gatun  the  difiference  of  85  ft.  between 
sea-level  and  the  lake  surface  will  be  overcome  by  a  flight  of  three 
locks,  that  is,  the  locks  are  directly  connected,  without  inter- 
vening basins,  and  form  a  continuous  structure.  They  are  built 
in  duphcate,  which  requires  the  construction  of  two  side  walls 
and  a  center  wall,  each  79  ft.  high.  The  side  walls  are  4,038  ft. 
long;  the  center  wall  is  extended  in  both  directions  to  provide 
guide  walls  for  vessels  entering  the  locks  and  is  6,330  ft.  in  length. 
An  outline  plan  and  typical  cross-sections  of  the  Gatun  flight  of 
locks  is  shown  on  Pig.  1,  Plate  I,  and  2,000,240  cu.  yd.  of 
concrete  will  be  used  in  their  construction. 

The  lock  sites  are  about  3,300  ft.  east  of  a  channel  that  was 
dredged  by  the  French  Company  from  Colon  to  Gatun,  and  as 
the  concrete  aggregates  were  to  be  obtained  from  points  on  the 
coast  and  transported  by  water  to  Colon,  it  was  considered  advis- 
able to  continue  this  method  of  transportation  to  Gatun  by  utiliz- 
ing the  French  Canal;  the  latter,  therefore,  at  once  became  a 
controlling  element  in  designing  the  handling  plant.  The  banks 
of  the  French  Canal  are  composed  of  an  alluvial  material,  with 
a  decided  tendency  to  slide,  and  were  considered  unsafe  for  the 
heavy  structures  and  storage  piles  required  at  the  unloading  point. 
A  boat  slip  was  therefore  dredged  in  firmer  ground  between  the 
canal  and  lock  sites  and  a  channel  excavated  to  a  connection  with 
the  French  Canal — ^incidentally  the  movement  of  the  unloading 
point  shortened  the  distance  between  the  storage  piles  and  mixing 
plant. 

Handling  Plant. — Referring  to  Figs.  2  and  3,  Plate  II,  it  is  seen 
that  the  entire  plant  is  composed  of  the  following  units,  each 
having  a  separate  and  distinct  function: 

1.  Facilities  for  unloading  and  storing  cement,  sand  and  stone. 


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346     Williamson  on  Handling  Concrete  at  Panama. 

Berm  Cranes, — Two  berm  cranes  only  were  used  at  Pedro 
Miguel,  but  the  booms  were  replaced  by  the  cantilever  arms  of  the 
other  two  so  that,  as  erected,  they  were  balanced  cantilever  cranes 
as  shown  in  Fig.  13,  Plate  VII.  Their  runway  tracks  were  so  located 
between  the  trestles  that  each  cantilever  extended  well  over  the 
respective  storage  piles;  both  cantilevers  were  equipped  with  trolleys 
operating  a  2i-cu.  yd.  excavating  bucket.  The  bins  from  the  other 
cranes  were  also  placed  on  these  two,  and  with  these  and  two 
cantilevers  the  facilities  for  handling  and  storing  sand  and  stone 
were   doubled.      Aside   from   the   above   changes   the   previous 


FIG.    12. — MIXING    CRANES    AND    STORAGE    TRESTLES,    PEDRO    MIGUEL    LOCKS. 

description  of  these  cranes  applies,  except  also  that  the  swinging 
platforms  were  omitted  and  the  mixers  emptied  into  buckets  on 
cars. 

Narrow-Gauge  Road. — The  track  system  of  the  narrow-gauge 
road  used  for  transporting  concrete  from  the  berm  to  chamber 
cranes  is  shown  in  Fig.  11.  The  difference  of  30  ft.  in  elevation 
between  the  forebay  and  lock  floors  was  overcome  by  means  of  an 
inclined  trestle  having  a  2.5  per  cent  grade.  The  tracks  were  laid 
with  70-lb.  rails  which  enabled  the  locomotives  to  attain  a  greater 
rate  of  speed  than  would  be  safe  on  the  lighter  rails  usually 
employed.      The    equipment    included    twelve    llj-ton    Porter 


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Plate  VII. 

Proc.  Nat.  Assn.  Cement  Users. 

Vol.  VIII,  1912. 

Williamson  on  the  Handling  of  Concrete 
IN  THE  Construction  of  the  Panama  Canal. 


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1  I  Miiffi 


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Williamson  on  Handling  Concrete  at  Panama.      347 

locomotives  and  24  steel-framed  flat  cars,  all  equipped  with  air, 
each  car  being  large  enough  to  hold  two  2-cu.  yd.  buckets. 

The  trains  were  composed  of  2  cars  and  each  car  carried  a 
bucket,  so  placed  that  when  alongside  a  berm  crane  each  bucket 
was  filled  from  the  corresponding  mixer  without  moving  the  train. 
Usually  the  trains  alternated  in  going  into  the  respective  lock 
chambers  and  stopped  under  the  first  chamber  crane;  the  crane 
placed  an  empty  bucket  and  picked  up  a  loaded  one  from  the 
same  car;  the  train  then  moved  to  the  next  chamber  crane  where 
the  operation  of  exchanging  an  empty  bucket  for  a  loaded  one 


FIG.    14. — GENERAL    VIEW    OF    LOCKS    AND    CHAMBER    CRANES,    PEDRO    MIGUEL 

LOCKS. 

was  repeated,  after  which  the  train  of  empty  buckets  returned  to 
the  mixers. 

Chamber  Cranes. — Two  chamber  cranes,  Fig.  14,  were  erected 
in  each  lock  at  Pedro  Miguel — they  placed  the  concrete  in  both 
side  and  center  walls.  Except  that  the  long  cantilever  arms 
extended  over  the  side  walls  and  the  short  ones  over  the 
center  wall,  the  description  of  them  given  for  the  Miraflores  plant 
applies. 

Concrete  Forms, — The  same  type  of  forms  was  used  here  and 
at  Miraflores,  in  fact,  all  of  the  steel  forming  and  some  of  the  wood 
forms  were  used  fiirst  at  Pedro  Miguel  and  later  at  Miraflores. 


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348      Williamson  on  Handling  Concrete  at  Panama. 

Auxiliary  Mixing  Plant, — Delays  in  the  delivery  and  erection 
of  the  permanent  plant,  combined  with  the  desire  to  increase 
the  rate  of  placing  concrete  led  to  the  erection  of  auxiliary  mixing 
plants  for  the  Pacific  locks.  At  Pedro  Miguel  a  2-cu.  yd.  mixer 
was  first  temporarily  set  up  at  the  lower  end  of  the  west  wall  and 
later  ipoved  to  a  similar  position  as  regards  the  east  wall,  where  it 
continued  work  until  December  16,  1911.  Two  2-cu.  yd.  cube 
mixers  were  installed  under  the  south  end  of  the  storage  trestle 
in  the  forebay  and  have  continued  in  operation  since.  In  all  of 
the  above  cases  the  mixers  were  on  hand,  having  been  ordered  for 
the  permanent  plant  as  applied  to  Miraflores  where  8  mixers  are 
required  as  against  4  in  the  application  of  the  plant  .to  Pedro 
Miguel.  In  each  location  the  mixers  were  charged  from  bins 
to  which  material  was  delivered  from  tracks  overhead,  by  standard 
railroad  dump  cars,  and  the  product  was  transported  to  the  walls 
by  narrow-gauge  equipment.  Half-yard  portable  mixers  are  also 
used  for  floor  construction  and  certain  portions  of  the  walls  where 
they  may  be  set  up  so  as  to  pour  concrete  directly  into  the  forms. 

The  stationary  mixers  located  in  the  east  wall  at  Miraflores 
have  been  previously  described.  As  they  are  for  the  purpose  of 
feeding  the  chamber  cranes,  and  it  was  necessary  to  purchase 
additional  mixers,  they  really  constitute  an  addition  to  the  per- 
manent plant,  made  for  the  purpose  of  increasing  its  efficiency. 
Aside  from  these  there  is  no  auxiliary  plant  used  at  Miraflores, 
except  the  half-yard  portable  mixers. 

PERFORMANCE  OF  PLANT. 

For  the  Pacific  locks,  crushed  stone  is  delivered  into  cars 
directly  from  the  quarry  bins  and  dumped  from  the  cars  on  the 
storage  trestles.  Sand  is  dredged,  loaded  into  barges  and  trans- 
ferred from  the  latter  to  bins  at  Balboa  with  electric  cranes,  it 
then  flows  by  gravity  from  the  bins  into  cars  for  transporting  to 
the  storage  trestles.  There  is  nothing  corresponding  to  the  unload- 
ing plant  at  Gatun,  therefore,  unless  it  is  the  crane  for  handling 
sand  at  Balboa.    Their  performance  is  given  in  Table  VII. 

Pedro  Miguel  Locks. 

Auxiliary  Plant, — The  placing  of  concrete  in  the  lower  guide 
wall  at  Pedro  Miguel  began  on  September  1,  1909,  with  a  mixing 


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352      Williamson  on  Handling  Concrete  at  Panama. 

plant  consisting  of  two  2-cu.  yd.  and  three  i-cu.  yd.  mixers.  The 
performance  of  this  equipment  to  Jmie  30,  1910,  working  on  an 
8-hr.  day  basis,  is  detailed  in  Part  1  of  Table  VIII. 

During  the  fiscal  year  ending  June  30,  1911,  the  auxiliary 
plant  consisted  mainly  of  three  2-cu.  yd.  mixers,  one  located  at 
the  south  end  of  the  east  wall  and  two  in  the  forebay,  the  half- 
yard  having  been  transferred  to  Miraflores.  It  placed  121,530 
cu.  yd.  and  the  detailed  performance,  on  an  8-hr.  day  basis,  is 
shown  in  Part  2  of  Table  VIII;  and  the  detailed  performance, 
on  an  8-hr.  day  basis,  of  this  plant  for  the  first  seven  months  of 
the  fiscal  year  ending  June  30,  1912,  is  shown  in  Part  3  of  the  same 
table. 

Permanent  Plant, — One  berm  and  two  chamber  cranes,  or 
one-half  of  the  plant,  began  operating  on  April  4,  1910  (a  chamber 
crane  placed  some  concrete  from  auxiliary  mixers  in  March); 
the  other  half  began  on  July  15,  1910.  The  portion  of  the  per- 
manent plant  in  operation  laid  73,083  cu.  yd.  prior  to  June  30, 

1910,  on  an  8-hr.  day  basis,  as  detailed  in  Table  IX. 

The  plant  worked  as  a  whole  from  July  15,  1910,  to  January 
31,  1911.  On  the  latter  date  the  dismantling  of  one  berm  crane 
began  preparatory  to  erecting  it  at  Miraflores.  The  dismantling 
of  two  of  the  chamber  cranes  for  the  same  purpose  began  on 
April  20  and  May  9,  1911,  respectively,  and  that  of  the  remaining 
berm  crane  on  May  19,  1911.  Two  chamber  cranes  remained  at 
Pedro  Miguel  until  December  12,  1911,  and  January  31,  1912, 
respectively,  being  used  in  the  meantime  for  placing  concrete 
from  auxiliary  mixers,  setting  iron  work  and  backfilling  the  middle 
wall.     The  plant  placed  379,190  cubic  yards  during  the  fiscal  year 

1911,  and  the  detailed  performances  of  the  berm  and  chamber 
cranes  respectively  are  given  in  Tables  X  and  XI. 

Miraflores  Locks, 

AiLCiliary  Plant. — Placing  concrete  in  the  floors  and  lateral 
culverts  of  the  upper  locks  at  Miraflores  was  begun  on  June  1, 
1910,  with  a  plant  consisting  of  two  ^-cu.  yd.  mixers,  and  1630  cu. 
yd.  were  placed  before  June  30,  1910. 

In  the  fiscal  year  ending  June  30,  1911,  the  auxiliary  plant 


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WlLUAMSON  ON  HANDLING  CONCBSTE  AT  PANAMA.        355 

consisted  of  two  2-cu.  yd.  mixers  located  under  the  north,  end  of 
the  east  storage  trestle,  and  four  i-cu.  yd.  mixers.  The  2-cu.  yd. 
mixer  plant  was  moved  to  the  east  wall  for  supplying  the  chambers 
cranes  in  May,  1911:  previous  to  this  it  supplied  a  berm  crane 
that  was  sufficiently  complete  to  place  concrete  with  the  boom, 
though  its  mixers  and  cantilever  arm  were  still  in  use  at  Pedro 
Miguel.  The  auxiliary  plant  handled  205,255  cu.  yd.  during  the 
year,  as  detailed  in  Table  XII;  and  a  similar  statement  giving  the 
detailed  performance  of  the  2-cu.  yd.  auxiliary  mixers  at  Mira- 
flores,  on  an  8-hr.  day  basis,  for  the  first  seven  months  of  the  fiscal 
year  ending  June  30,  1912,  appears  in  Table  XIII. 

Permanent  Plant. — One  berm  crane  without  cantilever  arm 
and  mixers  began,  in  its  uncompleted  condition,  to  place  concrete 
supplied  by  the  auxiliary  mixers  on  September  2,  1910,  and 
continued  placing  until  February  15,  1911,  when  it  was  taken  out 
of  commission  for  completion.  It  began  operating  again,  as  a 
complete  machine,  on  March  22,  1911,  and  a  second  berm  crane 
began  work  on  April  7,  1911.  With  these  67,774  cu.  yd.  were  laid 
previous  to  June  30,  1911. 

Other  units  of  the  plant  were  placed  in  commission  as  follows: 
2  chamber  cranes  on  July  13  and  August  3,  1911,  respectively, 
and  2  additional  berm  cranes  on  July  25  and  October  28,  1911, 
respectively.  There  are  2  more  chamber  cranes  under  erection  as 
follows:  Table  XIV  shows  the  performance  of  berm  cranes, 
Miraflores  Locks,  to  January  31, 1912,  and  Table  XV  the  perform- 
ance of  chamber  cranes,  Miraflores  Locks,  for  first  peven  months 
of  fiscal  year  ending  June  30,  1912. 

The  performances  of  the  Pacific  Division  plants  for  the  fiscal 
year  1911  are  given  by  the  Cost  Accountant  as  follows:  In  Pedro 
Miguel  locks  497,802  cu.  yd.  of  concrete  were  placed,  average 
division  cost  $4.70  per  cu.  yd.  and  385  cu.  yd.  of  reinforced  con- 
crete at  $17.74  or  a  total  of  498,187  cu.  yd.  at  $4.71  per  cu.  yd. 
In  Miraflores  locks  272,933  cu.  yd.  were  laid  at  an  average 
division  cost  of  $4.68  per  cu.  yd.  The  lowest  average  cost  for 
any  one  month  was  for  Pedro  Miguel  in  November,  1910, 
when  64,248  cu.  yd.  were  placed  at  $4.20  a  cu.  yd.  and  for  Mira- 
flores in  May,  1911,  when  36,154  cu.  yd.  were  placed  at  $4.05  per 
cu.  yd. 


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WiLUAMSON  ON  HaNSUNQ  CONCRETE  AT  PaNABIA.        359 


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360     Williamson  on  Handling  Concrete  at  Panama. 

The  detailed  division  cost  for  the  year  is  given  for  Pedro 
Miguel  as  follows: 

Concrete  (495,037  cu.  yd.): 

Cement $1 .5365 

Stone 8242 

Sand 3729 

Mixing 1771 

Total  cost  of  concrete $2.9107 

Large  rock  (2,765  cu.  yd.) $1 .  1483 

Masonry  (497,802  cu.  yd.): 

Concrete $2.8945 

Large  rock 0064 

Forms 4387 

Placing 3118 

Reinforcements 0367 

Pumps 0343 

Power 0454 

Maintenance  of  equipment 1723 

Plant  arbitrary 6847 

Division  expense .0792 

Total  division  cost $4.7040 

The  division  costs  per  month  since  June  30,  1911,  have  been 
as  follows: 


Cost 
Pedro  I 

per  Cubic  Yard  of  Concrete. 

Month.  1911. 

^iigucl. 

Miraflores. 

Plain. 

Reinforced. 

Plain. 

Reinforced. 

Julv 

$5.82 
5.63 
6.08 
6.26 
5.80 
6.27 

$6.26 
8.74 

11.91 
8.85 
9.94 
8.98 

$4.93 
4.45 
4.41 
4.50 
4.89 
5.06 

August r     r    T    T    .    T 

$11.17 

September 

October 

16.32 
21  39 

November 

December 

23.76 
14.45 

It  is  obvious  from  the  tables  that  a  large  percentage  of  delays 
in  placing  concrete  at  both  Gatun  and  the  Pacific  locks  is  charge- 
able to  forms.  At  times  the  forms  are  filled  so  rapidly  that  it  is 
difficult  to  keep  them  ahead  of  the  placing,  but  the  greatest  loss 
of  time  is  occasioned  by  the  amount  and  complication  of  forms  for 
the  electrical  tunnels,  conduits  and  machinery  rooms  near  the 
tops  of  the  walls.  The  records  given  for  the  Miraflores  plant  are 
not  representative,  as  the  entire  plant  is  not  in  operation. 


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USE  OF  CONCRETE  IN  THE  FOURTH  AVENUE 
SUBWAY. 

By  Frederick  C.  Noble.* 

The  Fourth  Avenue  Subway,  Brookljna,  is  an  example  of  the 
use  of  remforced  concrete  on  a  large  scale.  The  portion  now 
under  construction  extends  about  four  miles  from  the  Brooklyn 
end  of  the  new  Manhattan  Bridge,  over  which  it  is  intended  to 
connect  with  a  subway  system  in  Manhattan.  The  route,  Fig. 
1,  lies  through  Flatbush  Avenue,  Fulton  Street,  Ashland  Place 
and  Fourth  Avenue,  to  Forty-third  Street;  in  a  direction  generally 
south.  From  here  it  is  proposed  to  extend  it  in  future  by  two 
branches  to  the  southern  limits  of  the  borough.  The  subway 
is  being  built  for  the  City  of  New  York,  under  the  supervision 
of  a  state  commission,  with  Mr.  Alfred  Craven  as  the  chief 
engineer.  The  work  was  divided  into  six  contract  sections,  which 
were  let  in  November,  1909,  at  an  aggregate  price  of  about  $15,- 
000,000.     Construction  is  now  nearly  finished. 

The  structure  normally  has  space  for  four  tracks;  two  for 
local  and  two  for  express  service.  These  are  increased  to  seven 
and  eight  in  places  where  connection  spurs,  for  future  extensions, 
are  provided  in  two  levels  to  avoid  turnouts  at  grade.  There 
are  six  local  and  two  express  stations,  with  platforms  long  enough 
to  accommodate  ten-ear  trains. 

The  excavation  was  principally  in  a  moraineal  deposit,  con- 
sisting of  sand  with  more  or  less  gravel  and  boulders.  No  rock 
was  found  anywhere  on  the  line.  Some  quicksand  was  met 
near  the  middle  of  the  route,  where  the  subway  traverses  ground 
filled  in  over  the  bed  of  an  old  salt  marsh.  Ground  water  was 
encoimtered  at  or  near  tide  level  and  was  controlled  by  pumping. 
Excavation  was  usually  carried  on  under  covered  roadways,  but 
in  the  extension  of  Flatbush  Avenue  open  excavation  was  per- 
mitted. 

In  connection  with  the  work  it  was  necessary  to  underpin 


*  Division  Engineer.  Public  Service  CommiMion,  Broolclyn.  N.  Y. 

(361) 


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362    Noble  on  Use  of  Concrete  in  Brooklyn  Subway. 

about  forty  buildings  with  masonry  piers  to  sub-grade  in  advance 
of  the  excavation,  where  it  approached  close  to  and  below  their 
foundations.  It  was  necessary  also  to  temporarily  support  the 
elevated  railway  on  Fulton  Street  and  to  drift  a  crossing  under 
the  present  subway  in  operation  in  Flatbush  Avenue.  Since 
Fourth  Avenue  lies  along  the  foot  of  a  considerable  drainage 
area,  sloping  from  Prospect  Park,  it  was  necessary  to  depress  or 
intercept  many  cross-sewers  carrying  a  heavy  storm-flow,  and 
to  provide  under-grade  crossings  at  intervals.     About  six  miles 


Fia.  1. — PLAN  OF  FOURTH  AVENUE  SUBWAY,  BROOKLYN,  N.  Y. 

of  sewers,  of  all  sizes  up  to  9i  ft.  diameter,  were  thus  built  or 
rebuilt. 

The  typical  four-track  section  is  shown  by  Fig.  2.  The  roof, 
sides,  intermediate  walls  and  floor,  where  below  ground  water, 
are  reinforced  with  bars  ranging  between  li  and  f  in.  square. 
The  design  provides  for  a  uniform  live  load  of  300  lb.  per  sq.  ft. 
at  the  street  surface.  Waterproofing  is  used  at  stations  on  the 
roof  and  sides  and  generally  below  ground  water  on  the  sides  and 
floor.  Elsewhere  the  concrete  is  relied  on  for  sufficient  protec- 
tion against  seepage. 

The  amount  of  concrete  required  is  somewhat  over  400,000 


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Noble  on  Use  op  Concrete  in  Brooklyn  Subway.    363 

cu.  yd.  The  usual  proportions  are  1  to  2J  to  4J.  Much  of  the 
excavated  sand  is  suitable  for  concrete  and  is  used  accordingly. 
The  remainder  is  washed  or  dredged  sand  from  the  north  shore 
of  Long  Island.  The  aggregate  is  mostly  washed  or  dredged 
gravel  from  the  same  source,  usually  under  1  in.  and  well  graded 
in  size.  At  times  when  gravel  is  not  readily  obtainable,  cobbles 
and  fragments  of  boulders  are  crushed  and  used.  The  concrete 
is  mixed  rather  wet  to  facilitate  its  flowing  around  the  reinforce- 
ment, as  this  is  generally  spaced  quite  close. 

Reinforcing  rods  were  required  to  be  deformed.      Trans- 


OMiriM  IOO^Iam 


SMtioii  Ml  DryGrMBd. 


TkiekMSS  •!  concrete  and  spocin^ 
of  rods  ore  ^ivtn  for  nlnimwiB  cover,  ond 
ciiaajo  whort  cofor  aCMtfo  7  ft. 


^ 


FIG.  2. — TYPICAL  POUR-TRACK  SECTION  OP  SUBWAY. 

verse  and  longitudinal  rods  were  wired  at  their  intersections 
(Fig.  8).  For  this  purpose,  special  devices  of  bent  wire  were 
used;  these  served  at  the  same  time  to  space  the  rods,  or  to  hold 
them  at  the  proper  minimum  distance  from  the  forms.  Where 
imusually  long  spans  or  concentrated  loads  occurred,  the  roof 
was  of  girder  and  jack-arch  construction.  To  hold  the  thin 
covering  of  concrete  imder  the  lower  flanges,  special  clips  or 
hangers  of  twisted  wire  were  attached  at  intervals  by  bending 
them  over  the  upper  sides  of  the  flanges.  Sometimes  a  strip  of 
coarse  wire  mesh  was  wrapped  loosely  around  the  flanges  to 
serve  the  same  purpose.     In  a  few  instances,  where  the  concrete 


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364     Noble  on  Use  of  Concrete  in  Brooklyn  Subway. 

under  the  flanges  tapped  hollow,  it  was  chipped  off  around  the 
edges  of  the  flange,  and  a  strip  of  wire  mesh  was  attached  and 
covered  with  mortar  blown  in  place  by  means  of  a  cement  gun. 

Concreting  was  permitted  throughout  the  winter,  except 
on  the  very  coldest  days.  Materials  were  heated  by  fires  or 
steam  coils,  and  the  freshly  laid  concrete  was  covered  with  salt- 
marsh  hay  and  tarpaulins.  Salamanders  were  placed  under  the 
roof  forms  in  some  places.  On  accoimt  of  the  varying  condi- 
tions of  mixing  and  degree  of  exposure,  it  was  impracticable  to 
devise  a  set  of  rules  to  fit  all  cases;  but  the  criterion  was  held  to 
be  the  temperature  at  which  the  mixture  could  be  deposited  in 
the  forms. 

Roof  forms  were  struck  as  soon  as  the  temperature  condi- 
tions and  setting  qualities  of  the  particular  brand  of  cement 
used  would  permit.  As  this  was  a  factor  limiting  progress,  espe- 
cially in  the  case  of  large  steel  forms,  it  was  desirable  to  strike 
them  as  soon  as  practicable.  In  summer  they  were  struck  after 
80  hours,  and  in  exceptional  cases  even  at  50  hours,  but  in  winter 
it  was  sometimes  necessary  to  wait  a  week  or  10  days  before 
striking. 

The  methods  of  mixing  and  handling  concrete  vary  between 
the  diffei;pnt  sections  and  are  described  briefly  as  follows: 

Section  Af.  B.  Ex,  i,  extending  from  Nassau  Street  through 
Flatbush  Avenue  to  Willoughby  Street,  is  being  built  by  Smith, 
Scott  &  Co.,  contractors. 

Materials  for  concrete  are  brought  on  the  work  over  a  tram- 
way extending  along  each  side  of  the  cut  from  a  dock  \mder  the 
Manhattan  Bridge.  Sand  and  gravel  are  loaded  at  the  dock  in 
side-dump  cars,  drawn  by  20-ton  dinky  locomotives.  The  cars 
are  run  up  an  incline  and  dumped  into  bins  over  the  mixer,  which 
is  located  about  centrally  on  the  section.  This  is  a  li-yd.  machine, 
operated  by  a  30-h.p.  electric  motor.  The  mixture  is  discharged 
at  the  track  level  into  bottom-dump  cars  of  1-yd.  capacity,  in 
trains  of  3  or  4  cars,  hauled  to  the  point  of  deposit  and  dumped 
in  frame  chutes  through  which  it  slides  to  the  forms. 

As  the  sides  of  the  cut  were  almost  self-sustaining  and  as 
the  contract  terms  allowed  open  excavation  on  this  section,  very 
little'  cross-timbering  was  necessary;  a  condition  that  greatly 
facilitated  the  erecting  and  moving  of  forms.     The  forms  were 


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Noble  on  Use  of  Concrete  in  Brooklyn  Subway.     365 

of  the  collapsing  pattern,  with  stiffened  steel  sides  and  wood  top 
to  suit  the  varying  widths  of  roof.  The  floor  having  been  laid 
for  the  entire  width  of  structure,  and  the  reinforcement  placed 
for  the  sides  and  intermediate  walls,  the  forms  were  moved  into 
place,  one  20-ft.  section  at  a  time,  traveling  on  tracks  laid  on  the 
floor.  In  this  way  it  was  possible  to  lay  concrete  for  the  walls 
and  roof  over  four  tracks  in  sections  20  ft.  long  at  a  continuous 
operation.  These  forms  were  very  similar  to  those  used  on  one 
of  the  lower  sections,  in  which  connection  they  will  be  more  fully 
described. 

Where  structural  roof  framing  was  substituted  for  rod  con- 


no.  3. — COLLAPSIBLE  JACK  ARCH  FORMS. 

struction,  centering  (Fig.  3)  was  used  to  turn  the  jack  arches. 
These  were  of  angle-stiffened  plate,  with  an  adjustable  center 
strip  of  wood  for  varying  the  span,  and  were  set  in  position  on 
falsework.  The  span  was  maintained  by  tumbuckle  ties,  which 
also  served  to  draw  in  the  sides  on  striking  the  forms.  After 
striking,  each  section  was  lowered  with  a  winch. 

Section  Q-C-l,  extending  from  Willoughby  Street  along 
Flatbush  Avenue  and  Fulton  Street  to  Ashland  Place,  is  being 
built  by  William  Bradley,  contractor. 

Materials  for  concrete  are  delivered  at  a  large  yard  along- 
side the  subway  between  Third  and  Sixth  Streets,  where  the 
contractor  has  a  cement  storehouse  and  a  stable  for  his  horses. 


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366    Noble  on  Use  of  Concrete  in  Brooklyn  Subway. 

Teams  are  employed  for  moving  all  materials.  Concrete  was 
mixed  principally  by  a  gravity  mixer  located  in  the  cut.  Storage 
bins  for  sand  and  gravel  were  placed  just  below  the  street  level. 
These  fed  4  loading  hoppers,  each  of  one-bag-batch  capacity. 
After  moistening,  the  contents  were  dropped  successively  through 
three  mixing  hoppers,  receiving  the  full  dose  of  water  in  the  first 
one.  The  middle  hopper  was  slightly  offset  from  the  other  two. 
The  mix  was  discharged  at  the  bottom  level  into  cars  which 
were  nm  onto  a  cage,  hoisted  above  the  street  surface,  and  dumped 
into  an  overhead  bin.  From  the  bin  it  was  almost  immediately 
discharged  through  a  gate  into  tight  rear-dumping  steel  carts 
of  about  If-yd.  capacity,  which  were  teamed  to  the  point  of 
deposit.  The  mixture  was  dumped  on  hopper  platforms  and 
conveyed  through  8-in.  telescopic  chutes  to  the  forms.  The 
opening  at  the  bottom  of  the  hopper  was  closed  by  a  spatula  until 
the  entire  load  was  cleared. 

Most  of  the  structmre  on  this  section  is  of  steel  bent  and 
jack-arch  construction,  so  that  no  unusual  form-work  was  re- 
quired. The  reversion  to  this  older  type  of  design  was  at  the 
request  of  the  contractor,  and  partly  because  of  the  concentrated 
loadings  brought  by  the  elevated  structure  and  building  foimda- 
tions  to  be  supported  permanently  on  the  roof. 

Sections  11-E-l  and  11-A-l,  which  together  form  one  con- 
tract section,  extend  from  Fulton  Street,  through  Ashland  Place 
and  Fourth  Avenue,  to  Sackett  Street,  and  are  also  under  con- 
tract with  William  Bradley. 

The  methods  of  mixing  and  placing  concrete  are  the  same 
as  those  described  for  this  contractor's  adjoining  section.  The 
form  of  construction  is  also  similar,  except  where  the  line  passes 
by  a  curve  under  the  present  subway  in  Flatbush  Avenue.  Here 
the  design  is  of  massive  concrete  arches,  one  for  each  track, 
without  reinforcement  (Fig.  4). 

Section  ll-A-^,  from  Sackett  Street  along  Fourth  Avenue 
to  Tenth  Street,  is  being  built  by  the  E.  E.  Smith  Contracting 
Company. 

Materials  for  concrete  are  stored  in  a  yard  beside  the  Gowanus 
Canal  at  Third  Street,  and  are  distributed  to  the  work  by  mule 
teams.  Concrete  is  mixed  in  the  roadway,  directly  over  the 
point  of  deposit,  in  five  small  readily-shifted  drum  mixers  of 


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Noble  on  Use  of  Concrete  in  Brooklyn  Subway.    367 

i-yd.  capacity,  each  operated  by  a  15  to  25-h.p.  electric  motor. 
The  mixture  was  discharged  and  conveyed  to  the  forms  through 
10-in.  sectional  chutes  of  12-gauge  iron,  with  a  funnel  at  the  top. 

Generally,  the  floor  and  walls  of  the  westerly  two  tracks 
were  built  first,  then  the  floor  and  walls  of  the  easterly  two;  after 
which  the  roof  was  carried  across  all  foiu-  tracks  in  sections  about 
30  ft.  long.     Five  such  sections  would  be  in  progress  at  one  time. 

The  necessity  for  maintaining  the  cross-bracing  of  the  trench 
precluded  the  use  of  large  forms  such  as  were  used  on  certain  of 
the  other  sections.  Forms  were  made  of  2-in.  lumber,  dressed 
all  sides,  and  with  dapped  edges.     They  were  assembled  in  well- 


FIG.    4. — TYPICAL   SECTION   THROUGH    SUBWAY    AT   TUNNEL    UNDER    PLATBUSH 

AVENUE. 

braced  panels  and  could  be  used  many  times.  Jack-arch  forms 
(Fig.  5)  were  made  of  16-gauge  iron,  nailed  on  wood  ribs  and 
were  suspended  in  position  by  long  bolts. 

On  this  section  the  usual  waterproofing  on  sides  and  bottom 
below  ground  water  level  is  omitted.  In  such  situations  the  con- 
crete is  locally  made  richer,  1-2-4,  and  the  longitudinal  rein- 
forcement is  doubled  (Fig.  2). 

Section  11- AS,  from  Tenth  Street  along  Fourth  Avenue 
to  Twenty-seventh  Street,  is  under  contract  with  the  Tidewater 
Building  Company  and  Thomas  B.  Bryson. 

Materials  for  concrete  are  brought  on  scows  to  a  dock  at 


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368    Noble  on  Use  of  Concrete  in  Brooklyn  Subway. 

the  foot  of  Nineteenth  Street,  from  which  a  3-ft.  tramway  leads 
to  the  cut  and  through  it  in  both  directions.  The  sand  and 
gravel  are  transferred  from  the  scows  to  overhead  bins  by  a  crane 
and  clam-shell  bucket.  The  bins  discharge  through  gates  into 
4-yd.  side-dump  cars.  These  are  hauled  by  a  20-ton  locomotive 
to  the  main  storage  bins,  of  about  3,000  cu.  yd.  capacity,  situated 
in  the  cut  near  Nineteenth  Street  near  the  mixing  plant.  Belt 
conveyors  run  under  the  gates  of  the  bins  and  take  the  material 
to  a  bucket  elevator  which  raises  it  to  bins  over  the  mixer.     The 


FIG.   5. — METAL  JACK   ARCH   FORMS. 

overhead  bins  feed  into  measuring  hoppers,  where  the  cement  is 
added,  and  thence  into  the  mixer,  which  is  a  1-yd.  machine  mixing 
a  5-bag  batch.      Conveyors  and  mixer  are  electrically  driven. 

Taking  advantage  of  the  firm  character  of  the  ground  and 
the  great  width  of  the  avenue,  a  method  of  excavation  was  adopted 
that  dispensed  with  cross-bracing;  thus  leaving  the  cut  (Fig.  6) 
imobstructed  and  making  it  feasible  to  construct  large  sections 
at  one  time.  The  floor  of  the  two  middle  Iracks  was  laid  firet, 
and  this  was  followed  by  the  floor  and  duct  bench  of  each  of  the 
two  outside  tracks.  Concrete  was  brought  from  the  mixer  for 
this  part  of  the  work  in  2-yd.  side-dump  cars.     On  the  eomple- 


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Noble  on  Use  of  Concrete  in  Brooklyn  Subway.     369 

tion  of  a  section  of  the  bottom,  steel  forms  were  moved  into  place, 
and  the  sides,  intermediate  walls  and  roof  were  concreted  con- 
tinuously in  a  long  section. 

The  steel  forms  (Fig.  7)  were  of  the  collapsible  type,  made 
of  iV"ii^'  plate  and  stiflfened  with  shapes.  They  were  composed 
of  5-ft.  units,  bolted  together  in  sections  40  ft.  long,  and  traveled 
on  rails.  Four  such  sections,  one  for  each  track,  made  up  a  set 
of  forms;   of  which  two  were  in  use  generally  on  different  parts 


i 

*  ^ 

p 

z. 

^^^^^^HS^MlBkbf  'i^9Sl^^^^3Bp^H^^V^ 

\ 

i 

HKS^  jIHbis^ 

A 

FIG.  6. — METHOD  OF  OPEN  CUT  EXCAVATION. 

of  the  work.  The  forms  were  struck,  each  section  separately, 
by  means  of  a  hand  tackle  arrangement  that  swimg  the  top 
leaves  down  around  hinges  at  each  side,  and  drew  in  the  tops  of 
the  side-panels  automatically.  The  vertical  reinforcement 
(Fig.  8)  for  the  next  section  being  set  up,  the  forms  were  then 
pulled  ahead,  one  40-ft.  section  at  a  time,  by  a  locomotive,  into 
its  new  position;  an  operation  that  could  be  performed  in  a 
very  few  minutes.  As  each  section  was  advanced  it  was  adjusted 
to  exact  position  and  connected  to  its  neighbor  by  long  bolts  and 


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370    Noble  on  Use  of  Concrete  in  Brooklyn  Subway. 

pipe  separators.  The  adjustment  was  effected  by  the  jack- 
screws  and  sliding  axles  of  the  trucks;  affording  a  range  of  move- 
ment both  vertically  and  horizontally.  The  reinforcing  bars 
of  the  roof  were  then  laid  in  position. 

For  concreting  the  roof,  the  mixer  discharged  into  trains 
of  4  or  more  2-yd.  bottom-dump  buckets  on  flat  cars,  which  were 
pushed  by  a  locomotive  over  the  tramway  through  the  cut  to  the 
forms.      Here  the  buckets  were  lifted   by  a  locomotive  crane 


FIG.   7. — COLLAPSIBLE   STEEL   FORMS   FOR   ROOF   AND   SIDES. 

(Fig.  6),  and  dumped  on  a  hopper  raised  about  12  ft.  above  the 
forms.  From  the  hopper  the  mixture  flowed  through  shallow 
troughs  to  the  points  required.  When  both  sets  of  forms  were 
joined  together,  an  80-ft.  section,  requiring  over  600  cu.  yd., 
could  be  concreted  in  about  15  hours. 

Section  ll-A-4,  from  Twenty-seventh  Street  along  Fourth 
Avenue  to  Forty-third  Street,  is  being  built  by  the  E.  E.  Smith 
Contracting  Company,  who  are  also  the  contractors  for  section 
ll-A-2. 


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Noble  on  Use  of  Concrete  in  Brooklyn  Subway.     371 

Materials  are  delivered  into  bins  in  the  contractor's  yard 
at  Thirty-first  Street  and  Second  Avenue,  where  there  is  also  a 
cement  storehouse  of  30-cars  capacity  to  serve  both  sections. 

The  methods  of  mixing  and  distributing  concrete  and  the 
use  of  forms,  are  the  same  as  those  described  for  section  ll-A-2. 

All  cement  is  inspected  at  the  mills  and  shipped  in  sealed 


no.   8. — VERTICAL   REINFORCEMENT. 

bags.  The  testing  laboratory  is  in  Allentown,  Pa.,  in  the  Lehigh 
Valley  district.  Over  half  a  million  barrels  are  required.  Under 
the  specifications,  preference  is  given  to  brands  whose  records 
show  continued  increase  in  strength  over  long  periods.  As  a 
criterion  of  this  quality,  mortar  briquettes  are  required  to  show 
a  gain  of  at  least  50  lb.  between  the  7  and  28-day  tests. 


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THE    USE    OF    REINFORCED    CONCRETE    IN    HYPO- 
CHLORITE  WATER  PURIFICATION  WORKS. 

By  Walter  M.  Cross.* 

During  the  year  1911  an  experimental  installation  of  the 
hjT)ochlorite  process  for  the  approximate  sterilization  of  the 
entire  municipal  water  supply  of  Kansas  City  was  so  remarkably 
successful  in  diminishing  the  sickness  and  death  rate  in  the  city 
on  account  of  typhoid  fever  as  well  as  other  forms  of  intestinal 
disease,  that  the  Kansas  City  Fire  and  Water  Board  undertook 
the  construction  of  a  permanent  building  and  apparatus  for  the 
application  of  this  purification  process  to  the  water  supply. 

A  separate  building  was  constructed  to  make  possible  the 
satisfactory  storage,  handling  and  making  of  the  solution  of  hypo- 
chlorite ready  for  mixing  with  the  sedimented  water.  The  build- 
ing itself  was  designed  by  W.  C.  Root,  an  architect,  and  the  appa- 
ratus for  use  in  connection  with  the  sterilization  process  was 
installed  under  the  direction  and  supervision  of  Burton  Lowther, 
engineer  in  charge,  and  S.  Y.  High,  superintendent  of  the  Water 
Works  Department. 

The  apparatus  for  the  handling  of  the  hypochlorite  and  the 
supports  for  it  are  of  reinforced  concrete.  It  is  to  be  observed 
that  no  other  material  is  so  well  suited  for  use  in  connection  with 
this  sterilizing  agent  as  good  concrete  for  the  reason  that  all  other 
materials  that  are  capable  of  oxidation  are  promptly  attacked 
by  the  hypochlorite  solution  and  become  rapidly  deteriorated. 
The  prime  consideration  with  regard  to  this  class  of  installation 
is  to  employ  such  methods  of  construction  and  to  use  material 
that  is  so  permanent  in  character  as  to  obviate  the  necessity 
of  repairs  which  would  force  the  discontinuance  of  the  application 
of  the  sterilizing  agent  even  for  an  hour. 

The  basement  of  the  building  is  used  fcr  storage  of  the  reagent 
that  is  kept  in  reserve.  The  main  floor  is  used  to  house  the  dilu- 
tion tanks  and  the  feeding  devices,  while  on  the  floor  above  is 
placed  the  tank  in  which  the  hypochlorite  is  reduced  to  paste 

•City  Chemist.  KanBas  City.  Mo. 

(372; 


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Cross  on  Concrete  in  Hypochlorite  Plant.         373 

of  a  creamy  consistency  before  being  delivered  to  the  dilution 
tanks  beneath.  This  pasting  tank,  3  ft.  in  diameter  and  4  ft. 
high,  is  provided  with  a  stirring  device  carrying  two  rather  heavy 
rollers,  disposed  horizontally  at  its  lower  end.  The  rollers  clear 
the  bottom  of  the  concrete  tank  only  by  a  fraction  of  an  inch, 
thus  insuring  the  mashing  and  disintegration  of  all  of  the  small 
lumps  that  are  invariably  present  in  commercial  calcium  hypo- 
chlorite. Owing  to  the  fact  that  the  action  of  the  reagent  on 
bronze  is  to  form  on  the  surface  of  it  a  fairly  insoluble  and  pro- 
tective coating  of  metallic  carbonate  and  oxychloride,  that  metal 
appears  to  be  the  most  available  for  use  on  all  bearings  and  stirring 
or  disintegrating  devices  that  come  in  contact  with  the  solution. 
Leading  from  the  concrete  pasting  tank  are  pipes  so  arranged 
that  the  contents  of  the  tank  may  be  discharged  into  either  of 
the  large  dilution  tanks  on  the  floor  beneath.  The  outlet  of  the 
pasting  tank  is  placed  at  a  considerable  distance  above  its  bottom 
so  as  to  avoid  the  possibility  of  drawing  off  with  the  paste  any 
fragments  of  considerable  size.  The  pipes  carrying  the  paste 
are  so  arranged  as  to  be  readily  cleaned  in  a  few  minutes  in  the 
event  that  they  become  clogged.  Ultimately  they  are  sure  to 
become  clogged  if  they  are  not  occasionally  cleared  because  of  the 
formation  in  them  of  carbonate  from  carbon  dioxide  absorbed 
from  the  air. 

The  dilution  tanks  are  hexagonal  in  form,  9  ft.  in  maximum 
diameter  and  7  ft.  high;  the  walls  are  6  in.  thick.  Although 
the  difficulty  experienced  in  properly  disposing  the  reinforcing 
metal  in  the  construction  of  a  hexagonal  tank  is  much  greater  than 
is  the  case  in  the  building  of  a  round  one,  the  hexagonal  tank  is 
to  be  preferred  on  account  of  the  fact  that  in  a  round  tank  a 
rotary  stirrer  does  not  produce  nearly  such  thorough  agitation 
and  mixing  of  the  solution  of  hypochlorite  as  the  same  stirrer  can 
do  in  the  hexagonal  tank.  The  paste  is  mixed  with  water  in  the 
dilution  tanks  until  a  uniform  solution  of  a  strength  of  2  per  cent 
occurs.  The  use  of  the  two  tanks  makes  it  possible  to  accurately 
adjust  the  strength  of  the  solution  in  one  dilution  tank  while  the 
contents  of  the  other  are  being  utilized.  The  dilution  tanks  are 
placed  on  supports  high  enough  to  permit  the  use  of  a  gravity 
feed  to  the  orifice  box  which  is  placed  on  the  floor  of  the  room 
housing  the  big  tanks. 


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374         Cross  on  Concrete  in  Hypochlorite  Plant. 


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Cross  on  Concrete  in  Hypochlorite  Plant.         375 

Bronze  pipes,  1^  in.  in  size,  so  arranged  as  to  be  readily  cleaned 
in  the  event  of  stoppage,  connect  the  dilution  tanks  with  a  gauging 
tank,  4  ft.  in  diameter.  This  gauging  tank  contains  a  float, 
scale  and  pointer  so  arranged  that  the  man  in  charge  can  accu- 
rately check  the  speed  of  outflow  of  solution  from  the  orifice  box 
into  the  big  water  main  carrying  the  entire  city  water  supply 
from  the  settling  basins  to  the  pumps.  The  solution  passes  through 
the  gauging  tank  to  the  orifice  box.  Each  division  on  the  gauge 
represents  1  gallon  of  the  hypochlorite  solution. 

The  orifice  box  is  oblong  in  shape  and  carries  a  float  of  about 
250  cu.  in.  displacement.  The  float  operates  a  valve  which, 
by  either  opening  slightly  or  closing,  maintains  the  hypochlorite 
solution  in  the  orifice  box  to  a  constant  level.  One  end  of  the 
orifice  box  is  of  plate  glass  to  enable  the  operator  to  see  at  a  glance 
that  the  solution  is  filling  the  box  to  the  proper  height.  Attached 
to  the  plate  glass  and  covering  a  hole  in  it,  is  a  hard  rubber  disc 
having  near  its  periphery  several  slits,  the  adjustment  of  which  rep- 
resents the  size  of  a  stream  of  the  2  per  cent  hypochlorite  solution 
that  will  be  the  proper  amount  to  treat  the  quantity  of  water 
passing  through  the  main.  All  movements  of  the  hypochlorite 
solution  after  its  preparation  are  by  gravity.  Ample  opportunity 
for  the  hypochlorite  after  its  addition  to  the  water  to  react  with 
any  putrescible  organic  matter  and  germs,  is  afforded  during,  the 
time  in  which  the  water  passes  through  the  centrifugal  pumps,  the 
flow  line  and  a  small  storage  basin  at  Turkey  Creek  before  it  is 
pumped  to  the  domestic  water  users. 

All  of  the  stirring  devices  are  run  by  an  electric  motor  belted 
to  a  line  shaft  carrying  clutches  so  placed  as  to  make  possible 
the  running  of  any  one  of  the  stirrers  whether  or  not  any  of  the 
others  are  running. 

The  principle  involved  in  the  construction  of  practically 
all  hypochlorite  installations  for  the  purification  of  water  by  the 
oxidation  of  germs  and  putrescible  organic  matter  in  municipal 
water  supplies  is  substantially  the  same  as  that  in  Kansas  City. 
Concrete,  usually  reinforced,  is  universally  used  in  the  construc- 
tion of  all  permanent  apparatus  for  the  preparation  and  solution 
of  the  hypochlorite  for  mixing  with  the  water  to  be  purified. 

A  fairly  good  idea  of  the  disposition  of  the  various  parts  of 
the  purification  installation  is  given  in  Fig.  1. 


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DESIGN    AND    CONSTRUCTION    OF    THE    ESTACADA 

DAM. 

By  Hermann  V.  Schreiber.* 

Located  in  the  northwestern  section  of  the  country,  where 
fuel  costs  are  high,  it  is  natural  that  the  Portland  electric  com- 
panies should  have  early  appreciated  the  abundant  stream  flow 
characteristic  of  the  region,  which  results  from  the  high  precipi- 
tation on  the  western  slopes  of  the  Cascade  Mountains  and  in  the 
Willamette  Valley  and  which  was  rendered  available  for  their 
power  purposes  by  the  successful  development  of  high  tension 
electric  transmission  for  the  distances  involved  in  delivering  such 
hydro-electric  power  to  their  markets. 

The  first  plant  developed  to  serve  Portland,  and  one  of  the 
first  water-power  transmission  plants  on  the  coast,  is  located  at 
the  falls  of  the  Willamette,  adjacent  to  Oregon  City  on  the 
Willamette  River,  which  stream  flows  through  Portland  and 
empties  into  the  Columbia  River  about  six  miles  below  the  center 
of  that  city.  Some  years  later,  as  the  community  rapidly  grew 
in  size  and  industrial  activity,  a  combination  plan  was  projected 
by  interested  parties  for  the  construction  of  a  railway  and  power 
development  on  the  Clackamas  River,  based  upon  an  available 
power  site  some  forty  miles  east  of  Portland,  and  this  develop- 
ment has  since  been  completed  and,  with  the  other  railway  and 
lighting  interests,  has  been  included  in  a  consolidated  property 
known  as  the  Portland  Railway,  Light  and  Power  Company, 
which  at  present  supplies  practically  the  entire  electrical  market 
in  Portland,  including  the  local  and  interurban  railway  systems. 

Following  the  consolidation,  the  rapid  increase  in  the  power 
requirements  of  the  community  indicated  the  need  for  immediate 
additions  to  the  generating  capacity,  and  Sellers  and  Rippey, 
Consulting  Engineers  of  Philadelphia,  were  retained  by  the  finan- 
cial interests  in  control  of  the  consolidated  property  to  investi- 
gate and  report  upon  certain  features  of  the  existing  plants  and 

*  Sellers  and  Rippey,  Consulting  Engineers,  Philadelphia. 

(376) 


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SCHREIBER  ON   ESTACADA   CONCRETE   DaM.  377 

the  power  possibilities  and  costs  of  certain  new  developments 
which  were  suggested  for  consideration  from  time  to  time  during 
the  investigations.  Because  of  the  exceptional  water-power 
possibilities  of  this  region,  the  number  of  alternative  locations 
presented  for  consideration  was  greater  than  would  ordinarily 
come  within  the  radius  of  economical  transmission  to  a  large 
city,  but  attention  was  chiefly  directed  to  the  Clackamas  River, 
upon  which  the  company  already  owned  the  Cazadero  develop- 
ment, the  electric  railway  system  and  the  transmission  lines 
connecting  the  generating  station  with  Portland. 

This  stream  has  its  source  in  the  forest-covered  western 
slopes  of  the  Cascades  and  the  snow-covered  peaks  adjacent  to 
Mount  Hood.  The  run-oflf  resulting  from  the  high  precipi- 
tation peculiar  to  this  section  is  distributed  in  a  remarkably 
uniform  stream  flow  which,  because  of  the  favorable  geological 
formation,  is  maintained  even  during  the  long  dry  summer  sea- 
son. Consideration  was  primarily  given  an  available  site  for  a 
large  new  development  upon  property  already  owned  by  the 
company  on  this  river  above  the  existing  Cazadero  plant,  but 
investigations  extending  over  the  thirty  miles  of  the  river  down- 
stream to  its  mouth  revealed  a  site  capable  of  economic  develop- 
ment, which,  though  it  did  not  offer  as  large  capacity  as  the 
upper  site  suggested,  was  foimd  to  be  worthy  of  recommendation 
for  the  company's  immediate  consideration,  because  of  the  con- 
siderably lower  cost  involved  and  sufficient  size  to  meet  the 
immediate  power  requirements.  This  site,  by  far  the  most 
attractive  on  the  lower  river,  is  a  short  distance  below  the  com- 
pany's town  of  Estacada,  about  3^  miles  below  the  original 
development  at  Cazadero,  and  offered  the  advantages  of  a  rea- 
sonable head  for  direct  development  without  long  flumes,  acces- 
sible railway  connections  and  several  incidental  advantages  from 
a  construction  standpoint.  After  some  delay,  the  necessary 
property  was  acquired  and  executive  decision  given  that  the 
construction  proceed  without  delay.  Within  a  distance  of  a 
few  hundred  feet  several  possible  dam  sites  were  available,  giving 
the  same  head,  with  advantages  and  disadvantages  peculiar  to 
each,  making  the  proper  selection  one  of  considerable  difficulty. 
Fig.  1.  gives  a  general  view  of  the  Estacada  dam,  a  phn  of  which 
is  shown  in  Fig.  2. 


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378 


SCHREIBER  ON   EsTACADA   CONCRETE   DaM. 


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SCHREIBER   ON   ESTACADA  CONCRETE   DaM. 


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380  SCHREIBER  ON   ESTACADA  CONCRETE  DaM. 

It  is  of  considerable  interest  at  this  point  to  consider  further 
the  character  of  the  country,  its  geologic  history  and  bed-rock 
formation  as  affecting  the  selection  of  site,  preparation  of  founda- 
tions and  design  and  construction  of  dam. 

The  mountains  which  form  the  source  of  the  water  supply 
include  several  extinct  volcanic  peaks,  the  eruptive  discharge 
from  which  has  covered  the  country  for  miles  around  with  various 
forms  of  volcanic  debris  of  such  porous  and  uncertain  nature  that 
it  introduces  serious  obstacles  to  satisfactory  hydro-electric 
developments  of  any  considerable  magnitude,  even  when  they  are 
limited  to  the  use  of  a  low  dam  and  extended  canal  such  as  that 
which  has  been  installed  at  Cazadero.  In  order  to  properly  study 
the  situation  and  secure  all  possible  information  relative  to  the 
formation  of  this  material  which  now  constitutes  the  "bed  rock" 
a  careful  examination  of  this  section  was  made  on  request  by  Mr. 
J.  S.  Diller  of  the  U.  S.  Geological  Survey,  who  in  his  reports  on 
the  subject  made  the  following  statements: 

The  volcanic  breccia  (bed  rock)  is  made  up  of  unassorted  angular  frag- 
ments of  lava  andesite  and  basalt  of  various  colors  ranging  in  size  from  dust 
particles  and  grains  of  sand  to  large  rock  fragments  many  feet  in  diameter. 
This  fragmental  material  was  blown  by  explosive  eruption  from  the  volcanic 
craters  higher  up  on  the  range  and  fell  upon  the  mountain  slopes  where  it 
became  so  saturated  with  water  from  the  copious  rains  accompanying  the 
eruptions  that  it  flowed  in  great  steaming  sheets  from  the  Cascade  Range  to 
the  gentle  slope  of  the  plains,  in  much  the  same  way  as  similar  material 
flowed  down  the  old  stream  channels  on  the  western  slope  of  the  Sierra 
Nevada  in  California  and  covered  the  early  and  often  rich  deposits  of  aurif- 
erous gravels. 

Sheets  of  solid  nonfragmental  lava  forming  part  of  the  bed  rock  and  out- 
cropping on  the  slopes  of  the  canyon  occur  within  and  between  the  great 
sheets  of  volcanic  breccia.  Some  of  the  lava  sheets  are  basalt,  others  are 
andesite  and  they  are  usually  less  than  30  ft.  in  thickness.  The  basalts  are 
generally  very  porous  and  gray  or  dark.  The  andesites  are  often  reddish  and 
porphyritic  with  white  crystals  of  feldspar. 

The  depth  to  which  these  sheets  of  volcanic  breccia  and  lava  extend 
cannot  be  readily  determined  but  it  is  certainly  hundreds  of  feet  and  may  be, 
as  it  is  along  the  Santiam  and  McKcnzie  River  canyons,  over  a  1000  ft.  in 
thickness. 

Nearly  vertical  dikes  of  basalt  cut  up  through  the  sheets  of  volcanic 
breccia  and  lava  and  outcrop  on  the  surface.  These  dikes  in  some  places 
have  a  well  developed  columnar  jointing  which  divides  the  rock  into  columns. 
In  the  case  of  the  dikes  the  columns  lie  horizontally  and  extend  across  the 
dike.    In  the  lava  flows  the  columns  are  vertical,  but  in  all  cases  the  columnar 


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SCHREIBER  ON   ESTACADA  CONCRETE   DaM.  381 

joint  cracks  are  limited  to  the  dike  or  lava  sheet  and  do  not  extend  into  the 
adjacent  rock  nor  make  an  opening  of  great  extent.  There  is,  however, 
another  set  of  parallel  joints,  the  open  cracks  of  which  cut  up  through  the 
volcanic  breccia  and  sheets  of  lava  about  vertical  in  a  direction  approx- 
imately parallel  to  the  course  of  the  canyon.  Such  joints  may  be  of  consid- 
erable extent  and  form  important  openings  for  the  circulation  of  water; 
Such  joints  may  be  expected  and  should  be  carefully  looked  for  where  the 
rock  b  covered  with  soil  or  gravel.  It  is  especially  significant  that  the  dikes 
are  approximately  parallel  to  these  joint  cracks  and  suggest  that  the  joint 
cracks  may  extend  to  great  depths. 

The  conditions  that  confront  the  engineer  along  the  Clackamas  River 
in  the  volcanic  breccia  plain  region  are  very  much  the  same  as  will  be  found 
all  along  the  western  foot  of  the  Cascade  Range  from  the  Colxmibia  River  in 
Oregon  to  Feather  River  in  California,  one  of  the  most  import,ant  water- 
power  belts  in  the  United  States,  and  the  successful  solution  of  the  problem 
which  it  presents  at  one  point  will  greatly  facilitate  the  work  elsewhere. 

The  original  development  at  Cazadero  included  a  rock  fill 
timber  crib  dam  covered  on  the  up-stream  slope  with  a  large 
quantity  of  surface  soil  and  gravel,  used  to  reduce  to  a  minimum 
the  leakage  beneath  the  structure.  The  dam  creates  less  than 
one  half  the  operating  head,  the  balance  resulting  from  the  exten- 
sion of  a  head  race  canal  and  flume  about  If  miles  long  to  the 
generating  station,  the  tail  water  of  which  is  much  lower  than 
the  base  of  the  dam  because  of  the  intervening  slope  of  the  river. 
This  represents  a  conmion  method  of  development  in  the  West^ 
where  first  cost,  rather  than  low  operating,  maintenance  and 
depreciation  charges,  has  in  the  past  largely  governed  such  pro- 
jects. This  development  was  well  advanced  when  taken  over  by 
the  present  owners  and  as  completed  by  them  utilized  conditions 
advantageously,  although  it  possesses  in  a  degree  the  inherent 
disadvantages  of  such  construction  in  that  its  peak  load  capacity 
is  limited  by  the  forebay  pond  capacity  and  the  leakage  under  the 
dam  and  from  the  canal  tends  to  reduce  the  dry  season  plant 
capacity.  The  present  owners  have  however  succeeded  in  reduc- 
ing the  leakage  under  the  dam  to  a  trifling  amount. 

Considering  the  magnitude  and  permanence- of  the  consol- 
idated property,  it  was  felt  desirable  in  planning  extensions  to 
endeavor  to  provide  for  direct  power  developments,  creating  the 
entire  head  by  a  concrete  dam  affording  large  storage  reservoir 
capacity  and  locating  the  plant  directly  at  the  dam  without  inter- 
vening flume  or  canal,  thus  permitting  almost  indefinite  peak 


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382  SCHREIBER  ON   ESTACADA  CONCRETE  DaM. 

Joad  capacity  to  be  developed.  This  method  of  development 
involves  higher  dams  and  consequently  demands  greater  assur- 
ance concerning  the  security  of  foundations  and  before  asking 
Mr.  Diller  to  report  upon  the  geological  formation  core  drill 
investigations  were  started  to  determine  the  characteristics  of 
the  underlying  material.  His  report,  as  will  be  noted,  strongly 
confirmed  our  own  conclusions  as  to  the  importance  of  this  prob- 
lem and  we  continued  our  extensive  explorations  with  core  drills, 
going  as  deep  as  250  ft.  at  times,  and  not  content  with  a  partial 
examination,  we  made  investigations  at  considerable  cost  and 
trouble  in  the  river  bed  as  well  as  upon  both  banks. 

SITE. 

At  the  first  new  site  considered  for  the  development  of  power 
•on  the  Clackamas  River  above  Cazadero  it  was  proposed  to 
create  135  ft.  head  at  a  direct  connected  plant,  providing  large 
pond  storage  which  would  be  of  considerable  value  to  all  the 
plants  existing  or  constructed  at  any  future  time  on  the  river 
below  this  point. 

At  the  Estacada  site  below  Cazadero  it  was  proposed  to 
develop  power  under  83  ft.  head,  utilizing  all  the  available  fall  in 
the  river  in  the  3J  miles  below  the  original  Cazadero  power  sta- 
tion and  providing  pond  storage  which  would  be  of  great  value 
in  carrying  the  daily  peak  load. 

The  investigations  for  the  higher  head  development  at  the 
upper  site  were  started  before  the  lower  property  was  acquired 
and  were  under  the  direct  supervision  of  the  field  engineer,  Mr. 
Shirley  C.  Hulse,  under  our  direction.  The  very  thorough  study 
of  the  situation  there  gave  considerable  data  for  use  in  develop- 
ing a  method  of  treatment  to  insure  as  far  as  it  might  be  prac- 
ticable an  absolute  cut-oflf  across  the  canyon  which  would  prevent 
any  undue  leakage  or  erosion  of  the  river  bottom  after  completion 
of  construction,  and  the  results  of  this  work  were  immediately 
applied  to  the  Estacada  construction,  saving  much  time  in  the 
preliminary  engineering  there. 

When  the  company  was  ready  to  proceed  with  this  construc- 
tion the  work  was  very  urgent.  The  general  preliminary  inves- 
tigations covered  both  sides  of  the  river  for  a  distance  of  several 
hundred   feet;    well   drillings   were   made   without   finding   any 


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SCHREIBER  ON   EsTACADA  CONCRETE   DaM.  383 

radical  difiference  in  the  character  of  the  bed  rock,  except  that 
the  first  and  the  last  of  the  several  sites  considered  were  found  to 
be  underlaid  with  a  soft  clay  formation  which  might  have  neces- 
sitated a  reinforced  mat  or  piling  to  support  part  of  the  struc- 
tures. Of  the  four  sites  here  considered,  the  third  one  was  selected 
as  offering  an  island  which  it  was  expected  would  considerably 
reduce  the  amoimt  of  material  required  and  at  the  same  time 
make  the  construction  much  more  convenient  by  facilitating  the 
diversion  of  the  stream  through  the  rainy  season. 

Further  investigations  were  then  made  of  the  actual  condi- 
tions on  the  island  with  the  result  that  a  large  ravine  was  foimd 
to  extend  parallel  to  the  thread  of  the  stream,  which  being  filled 
with  debris  necessitated  its  entire  excavation.  As  the  construc- 
tion proceeded  the  left  end  of  the  island  adjoining  this  ravine  was 
found  to  contain  a  layer  of  clay  sloped  in  such  a  way  as  to  endan- 
ger its  stability  if  loaded  with  any  of  the  dam  superstructure. 
This  was  also  removed  and  with  the  removal  of  another  section 
of  the  island  on  account  of  the  great  uncertainty  of  the  effective- 
ness of  any  device  against  leakage  there  was  little  left  of  the 
island  and  no  expense  was  saved  by  its  use  in  the  construction. 


CUT-OFF  WALL. 

The  study  of  the  foundation  conditions  on  the  Clackamas 
River  was  evidenced  by  the  investigations  and  test  pits,  together 
with  rough  pressure  tests,  Mr.  Diller's  expressions  relative  to 
the  geological  formation,  and  the  general  hesitancy  among  engi- 
neers with  respect  to  constructing  high  masonry  dams  upon  such 
foimdations  confirmed  the  original  belief  that  somewhat  novel 
methods  must  be  adopted  to  give  reasonable  assurance  concern- 
ing the  integrity  of  the  work  to  be  constructed.  Moreover,  it 
was  evident  that  the  nature  of  these  methods  should  be  such  as 
to  permit  demonstration  of  their  efficacy  before  any  large  invest- 
ment in  the  construction  should  be  made,  and  this  involved  some 
experimental  work  and  expense  which  would  not  be  involved  on 
more  substantial  or  satisfactory  foundations. 

It  will  be  evident  that  impermeable  foimdations  are  desirable 
for  the  following  reasons: 

(a)  To  minimize  the  possibility  of  upward  pressure  under  the 


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384  SCHREIBER  ON   EsTACADA   CONCRETE  DaM. 

base  of  the  dam  superstructure.      (This  applies  chiefly  to  solid 
dams.) 

(b)  To  prevent  percolation  under  the  dam  which  might  lead 
to  sufficient  erosion  to  involve  undermining  of  the  structure. 

(c)  To  overcome  any  structured  weakn^ess  due  to  the  original 
geological  formation  and  properly  provide  a  support  for  the 
superimposed  load. 

(d)  To  avoid  waste  of  water  (the  chief  power  asset  of  the 
company)  from  the  reservoir,  through,  under  or  around  the  dam, 
instead  of  through  the  turbines,  thus  providing  K.W.H.  for  sale. 

To  satisfy  these  conditions  with  existing  foundations  of  the 
character  described  in  Mr.  Diller*s  reports  required  a  departure 
from  any  methods  heretofore  used  of  which  we  had  knowledge 
and  in  studjdng  the  problem  it  appeared  that  the  only  safe  pro- 
gram must  practically  provide  for  actually  changing  the  struc- 
tural character  of  the  underlying  formation.  It  occurred  to  our 
chief  engineer,  Mr.  S.  Howard  Rippey,  who  had  spent  some  time 
on  the  ground,  that  the  most  promising  method  would  be  the 
solidification  of  the  porous  material  by  the  introduction  of  cement 
grout  under  pressure,  but  that  the  success  of  the  work  must  be 
susceptible  of  demonstration  by  actual  test  before  the  super- 
structures should  be  started.  Thorough  inquiry  failed  to  disclose 
any  precedent  for  the  use  of  grout  for  the  general  treatment  of 
foundations,  although  it  was  foimd  that  cavities  in  limestone  rock 
under  the  New  Croton  Dam  had  been  filled  with  grout,  much  as  a 
dentist  would  fill  a  cavity  in  a  tooth.  The  grouting  method  had 
also  been  used  in  filling  back  of  lining  walls  in  tunnels,  etc. 
Notwithstanding  the  absence  of  precedent,  it  was  decided  to  pro- 
ceed with  a  grouting  scheme  and  a  program  was  outlined  for 
preventing  leakage  of  water  from  the  reservoir  created  by  the 
dam,  under  or  around  the  dam,  to  the  low  tail  water  level  below 
the  dam  and  the  experiments  which  should  be  made  to  properly 
demonstrate  the  efficacy  of  the  method  before  the  complete 
development  should  be  imdertaken  were  prescribed.  The  general 
idea  provided  for  drilling  a  double  line  of  holes  of  an  average 
depth  of  say  50  ft.  under  the  heel  of  the  dam  across  the  entire 
valley  to  and  under  the  shore  abutments  and  the  subsequent 
forcing  into  each  of  these  holes  of  grout  of  such  consistency  as  to 
percolate  through  the  entire  substructure  and  so  permeate  it  as 


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SCHREIBER  ON  EsTACADA  CONCRETE  DaM.  385 

to  solidify  it  absolutely  throughout  the  entire  length  of  the  super- 
structure, thus  making  the  foundations  absolutely  solid  and  the 
equivalent  of  a  deep  cut-off  wall. 

It  was  recognized  that  experiments  would  be  necessary  to 
determine  the  proper  spacing  of  the  grout  holes  and  their  depth, 
which  would  ensiu^e  sufficient  diffusion  of  the  grout  through  the 
varying  material  encoimtered  to  create  a  continuous  impermeable 
barrier,  thus  preventing  seepage  of  water  from  the  reservoir  imder 
the  hydrostatic  head  which  would  be  created  by  the  dam. 

After  drilling  the  double  line  of  holes,  the  program  con- 
templated the  test  of  each  hole  with  water  pressiu^e,  a  record 
being  kept  of  the  quantity  escaping  and  the  pressure  applied  to 
each  hole.  This  water  pressure  test  also  provided  for  washing 
out  the  interstices  ready  for  the  reception  of  the  grout.  Upon 
the  completion  of  the  tests,  the  cement  grout  was  to  be  pumped 
into  the  holes  imder  pressure  and  after  allowing  time  for  harden- 
ing, a  third  line  of  holes  was  to  be  drilled  midway  between  the 
first  two  or  outer  lines  and  tested  with  water  pressure.  The  idea 
was  that  if  water  pressiu^e  be  applied  to  the  center  holes  at  or 
slightly  above  the  hydrostatic  pressure  to  which  this  rock  would 
be  subjected  by  the  water  in  the  reservoir  after  completion  of  the 
dam  and  no  appreciable  leakage  occiured,  we  should  feel  rea- 
sonably certain  that  the  cement  grout  had  proven  effective  in 
making  the  entire  foimdation  impermeable. 

Before  purchasing  apparatus  to  handle  the  thin  cement 
grout  communication  with  several  pump  manufactiu*ers  showed 
that  in  so  far  as  the  manufacturers'  guarantees  were  concerned, 
choice  was  limited  to  two  standard  makes  of  hand-operated 
diaphragm  pumps  which  would  require  8  men  on  the  handles  to 
develop  a  pressure  of  100  lb.  per  sq.  in.  Only  one  power  dia- 
phragm pimip  was  offered  by  the  manufacturers  who  would 
assume  no  responsibility  for  its  successful  operation.  It  was 
foimd  that  in  both  this  and  foreign  coimtries  plimger,  diaphragm 
and  centrifugal  pumps  had  been  successfully  used,  but  after  care- 
ful study  of  all  the  commercial  pumps  available  it  was  decided 
that  the  use  of  compressed  air  would  be  more  effective,  flexible 
and  economical  than  any  mechanical  pump.  Having  eliminated 
the  question  of  pumps  it  was  foimd  that  several  different  types 
of  compressed  air  tanks  were  available;  some  being  provided  with 
different  numbers  and  shapes  of  blades  which  were  revolved  in 


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386 


SCHREIBER  ON  EsTACADA  CONCRETE  DaM. 


the  tank  for  the  mechanical  mixing  of  the  cement  grout  while  in 
others  the  grout  was  mixed  entirely  by  the  circulation  of  air. 

Interviews  were  had  with  a  number  of  contractors  and  engi- 
neers who  had  had  occasion  to  use  the  different  types  of  machin- 
ery and  it  was  finally  decided  to  purchase  the  Canniff  Pneumatic 
Grout  Mixer  and  Injector.  This  machine,  Fig.  3,  consists  of  a 
plate  steel  cylinder  with  a  conical  shaped  bottom  and  flat  plate 


Blow  off  when  nixing 


FIG.    3. — CANNIFF   PNEUMATIC   GROUT   MIXER   AND   INJECTOR. 

steel  top  which  is  provided  with  a  smaller  hinged  circular  lid 
opening  inward  through  which  the  water,  cement  and  sand  are 
introduced.  The  tank  is  provided  with  a  blow-off  valve  on  top 
of  the  lid,  also  an  air  inlet  pipe  tapped  into  the  side  near  the  top, 
a  grout  discharge  pipe  tapped  into  the  bottom  and  a  by-pass  pipe 
between  the  air  and  grout  pipes.  The  valves  are  so  arranged  that 
when  the  cement,  sand  and  water  are  placed  in  the  tank  the  com<< 


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SCHREIBER  ON  EsTACADA   CONCRETE  DaM.  387 

pressed  air  is  forced  into  the  bottom  of  the  tank  through  the 
grout  pipe  and  having  free  escape  through  the  blow-off  valve  at 
the  top,  the  grout  is  thoroughly  mixed  by  the  passage  of  air 
bubbles  through  it. 

When  it  is  desired  to  discharge  the  grout  the  valves  are 
so  manipulated  that  the  air  is  introduced  near  the  top  of  the 
tank  and  the  grout  forced  out  through  the  bottom  pipe,  the  press- 
ure being  limited  only  by  the  capacity  of  the  compressor  and 
the  strength  of  the  tank.  It  is  possible  to  connect  any  number 
of  these  tanks  on  to  one  main  grout  discharge  pipe,  thereby  insur- 
ing a  continuous  flow  of  grout  and  by  a  proper  system  of  pipe 
connections  any  one  tank  may  be  cut  out  for  repairs  without 
interfering  with  the  operation  of  the  remaining  tanks. 

After  experimenting  on  the  Estacada  foundations  with  both 
the  shot  and  diamond  core  drills,  an  equipment  of  7  Calyx  shot 
drills  was  finally  installed  and  operated  at  this  development 
night  and  day  for  a  period  of  about  one  year.  These  drills  gave 
a  hole  varjdng  from  2f  to  8  in.  in  diameter  depending  upon  the 
character  of  the  bed-rock  material. 

Where  possible,  in  advance  of  the  core  drilling  3-in.  wrought 
iron  pipe  casings  were  set  to  a  depth  of  from  4  to  6  ft.  in  the  rock 
and  grouted,  the  upper  ends  projecting  about  1  ft.  above  the 
surface  and  being  threaded  to  permit  the  attachment  of  the 
testing  and  grouting  apparatus.  While  the  original  plan  called 
for  grouting  in  advance  of  any  construction,  the  failure  to  start 
this  portion  of  the  work  at  once  tended  to  retard  the  actual  con- 
struction work  and  it  therefore  became  necessary  to  construct  a 
concrete  cut-off  wall  7  to  10  ft.  deep  and  set  the  casings  in  this 
wall  and  drill  the  holes  through  the  casings  into  the  rock  below 
where  this  was  necessary.  The  cut-off  wall  was  placed  upstream 
from  the  foot  of  the  dam  and  the  construction  of  the  dam  super- 
structure was  continued  without  interference. 

The  final  report  of  Mr.  Frank  R.  Fisher,  resident  engineer, 
for  the  Light  and  Power  Department,  Portland  Railway,  Light 
and  Power  Company,  imder  whose  supervision  the  Estacada  con- 
struction work  was  completed,  gives  the  following  additional 
detail  information  relative  to  the  conditions  which  existed  and 
methods  used  in  the  grouting: 

The  rock  mass  is  traced  throughout  with  Beams,  very  irregular  in  shape 
and  size,  extending  in  all  directions  with  but  slight  continuity.    They  vary 


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388  SCHREIBER  ON  EsTACADA  CONCRETE  DaM. 

from  an  almost  imperceptible  cleavage  joint  up  to  those  having  an  approx- 
imate width  of  from  one  to  two  inches,  the  large  majority  observed  meas- 
uring but  a  fraction  of  an  inch.  The  seams  are  more  or  less  choked  with 
sand,  gravel,  small  particles  of  rock,  and  other  debris.  No  large  crevices  or 
faults  were  found  at  the  site,  nor  observed  in  the  vicinity  of  the  dam. 

On  the  whole,  the  rock  gives  indication  of  possessing  fair  bearing  value, 
and  while  not  what  would  be  classed  as  hard,  would  probably  offer  consid- 
erable resistance  to  the  erosive  action  of  water,  except  under  high  velocities. 

The  plan  was  adopted  of  distributing  drills  over  a  wide  area  and  each 
hole  drilled  was  tested  and  grouted  immediately  on  completion  before  putting 
down  any  other  nearby  holes.  In  grouting,  the  method  usually  followed  was 
to  make  connection  between  the  grout  tanks  and  the  casing  by  means  of  a 
flexible  copper  hose,  and  introduce  the  grout  at  the  top  of  the  hole;  but  in 
order  to  prevent,  if  possible,  the  rapid  choking  of  the  hole  with  cement,  which 
frequently  occurred,  the  method  of  introducing  a  pipe  into  the  hole,  and  dis- 
charging the  grout  at  various  depths  was  tried  out.  For  this  purpose  a  2-in. 
pipe,  made  up  in  sections,  was  used,  and  the  operation  was  started  with  the 
same  inserted  to  within  a  few  feet  of  the  bottom  of  the  hole.  When  the  hole 
gave  evidence  of  tightening  with  the  pipe  in  this  position,  one  section  was 
detached,  usually  10  ft.  in  length,  thus  raising  the  outlet,  and  the  operation 
repeated.  At  intervals  a  charge  of  water  was  shot  in,  to  keep  the  pipe  from 
plugging,  and  also  to  loosen  up  the  cement  that  settled  in  the  hole.  This 
method  of  grouting  through  the  pipes  was  given  a  thorough  trial,  but  so  far 
as  could  be  observed  it  had  very  little  advantage  as  to  the  amount  of  grout 
the  hole  would  take,  over  the  less  laborious  operation  of  introducing  it 
directly  at  the  top.  The  changing  of  the  position  of  the  pipes  also  interrupted 
the  continuous  flow  of  the  grout,  which  it  was  desirable  to  maintain  in  order 
to  accomplish  the  best  results. 

The  consistency  of  the  grout  was  varied  to  meet  the  different  conditions, 
1  part  of  cement  to  5  of  water  appearing  to  give  the  best  results,  but  the 
proportions  tried  out  varied  from  1  cement  and  2  water  to  1  cement  and 
15  water. 

The  grout  was  forced  in  under  air  pressure  ranging  from  50  to  200  lb. 
per  sq.  in.,  depending  on  the  tightness  of  the  hole,  but  the  material  at  the 
lower  depths  would  not  tighten  up  beyond  a  certain  degree.  While  it  was 
desirable  to  use  the  higher  pressures,  in  order  to  accomplish  the  greatest 
diffusion,  it  was  not  always  practicable;  to  do  so,  on  account  of  it  blowing 
out  at  the  surface. 

As  the  general  nature  of  the  rock  had  been  investigated  through  the 
cores  from  the  preliminary  exploration  holes,  no  special  effort  was  made  to 
preserve  the  same  when  drilling  the  primary  holes.  That  from  the  proving 
holes,  however,  was  carefully  examined  for  any  traces  of  grout,  and  while 
some  very  fair  specimens  of  cement  core  were  obtained,  the  amount  was  not 
large.  This  was  probably  due  to  the  fact  that  most  of  the  seams  were  small, 
and  the  cement  entering  therein  would  be  ground  to  powder  under  the  action 
of  the  bit.  It  is  also  probable  that  in  many  instances,  at  the  time  the  prov- 
ing holes  were  put  down,  the  cement  had  not  set  sufficiently  hard  to  core. 


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SCHREIBER  ON  ESTACADA  CONCRETE  DaM.  389 

as  the  conditions  arising  from  the  various  stages  of  the  construction  work, 
as  well  as  the  rate  of  progress  to  be  maintained,  made  it  necessary  to  follow 
on  with  the  proving,  within  a  short  time  after  the  grouting  of  the  primary 
holes. 

The  pressure  testing  of  the  proving  holes  was  important  and  the  final 
plan  adopted  gave  a  direct  pressure  from  tanks  located  above  the  proposed 
pond  water  level  as  best  approaching  the  final  conditions.  After  the  piping 
was  filled,  a  test  run  of  ten  minutes  was  taken,  the  rate  of  seepage  per  minute 
being  averaged  and  recorded.  Besides  testing  individual  holes,  severs! 
combinations  were  tested  in  order  to  determine  if  possible  the  extent  of  inter- 
communication beneath  the  surface.  The  combined  seepage  in  this  was 
found  to  be  considerably  less  than  the  sum  of  the  separate  tests  and  in  some 
instances  was  only  about  half.  An  additional  refinement  was  introduced  by 
the  testing  of  each  proving  hole  in  some  sections  every  10  ft.  in  depth  as  it 
was  being  treated,  thereby  giving  an  indication  of  the  effectiveness  of  the 
grouted  cut-off  wall  at  different  depths.  In  some  instances  communication 
was  found  to  exist  between  holes  located  as  far  as  70  ft.  apart. 

After  the  completion  of  the  dam,  and  subsequent  filling  of  the  pond,  two 
test  holes  were  put  down  inside  of  the  dam,  approximately  30  ft.  from  the 
cut-off.  One  of  these  was  located  between  buttresses  Nos.  10  and  11  and  the 
other  between  Nos.  12  and  13,  opposite  the  weakest  points  in  the  grouted 
cut-off.  After  drilling  to  a  certain  depth,  backfiow  was  obtained  from  each, 
and  the  maximum  height  to  which  the  water  rose  in  an  extended  pipe,  due  to 
upward  pressure,  was  within  13  ft.  of  the  elevation  of  that  of  the  pond.  The 
results  of  these  tests  indicate  that  some  upward  pressure  exists  in  the  founda- 
tion material  in  this  locality,  which  the  mass  of  overlying  rock  is  resisting. 

The  excavation  of  a  supplementary  cut-off  trench  at  one  point  where 
grouting  had  previously  been  done  offered  excellent  opportunity  for  observing 
its  effects,  as  many  seams  were  exposed  and  all  of  them  proved  to  be  well 
caulked  with  cement. 

The  data  of  quantities  and  cost  of  this  portion  of  the  work  is  also  of 
interest. 

Drilling  555  Holes,  34,038  Pr.,  Costino   $1.55  per   Pt.  for  Drilling 

AND  Grouting. 
Labor — 

DrilUng $0.68 

Grouting 18 

Repairs 17 

Plant  (drills  and  grout  tanks) 30 

Cement 12 

Power 05 

Overhead  (incorporated  general  plant) 32 

Total $1.72 

Less  salvage 17 

$1.55 


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390  SCHREIBER  ON   EsTACADA  CONCRETE  DaM. 

In  one  section  of  the  work  the  original  pressure  tests  on  the 
ungrouted  holes  frequently  developed  a  seepage  of  over  100 
gallons  per  minute  per  hole  and  communication  existed  between 
holes  located  over  a  wide  area  and  surface  leakage  also  appeared 
in  many  places.  Where  the  original  primary  holes  gave  an 
average  leakage  before  grouting  of  80  gallons  per  minute,  thirteen 
proving  holes  when  drilled  showed  an  average  leakage  of  7  gallons 
per  minute.  Another  section,  for  the  first  30  ft.  of  depth  below 
the  concrete  cut-ofif  the  treatment  appeared  to  be  fairly  success- 
ful, but  at  the  full  depth  a  test  on  a  group  of  thirteen  proving 
holes  showed  an  average  seepage  of  6.4  gallons  per  minute.  In 
still  other  sections  the  proving  holes  showed  seepage  varying 
from  2.2  gallons  to  3.6  gallons  per  minute. 

A  total  of  1942  bbls.  of  cement  were  used  in  grouting.  The 
average  depth  drilled  per  hour  was  1.32  ft.,  including  time  for 
moving,  etc.  The  cement  pumped  into  the  holes  varied  from 
3.32  bbls.  to  50  bbls. 

This  treatment  indicated  the  possibility  of  constructing  what 
may  be  termed  an  effective  cut-off  without  being  literally  imper- 
vious. There  is  however  no  assurance  that  this  degree  of  success 
would  result  from  similar  work  on  another  Qite  with  this  kind 
of  foundation. 

DESIGN  OF  DAM. 

Previous  experience  in  the  construction  of  hollow  dams 
together  with  numerous  studies  of  comparative  costs  and  advan- 
tages inherent  in  hollow  and  solid  dams  prompted  us  to  recom- 
mend the  hollow  dam  for  use  in  this  instance  particularly  because 
of  the  character  of  the  foundations.  WhOe  several  other  forms 
of  hollow  dams  are  available  and  have  been  carefully  studied  and 
some  have  been  built,  the  distance  at  which  the  work  had  to  be 
directed  together  with  the  urgency  of  the  construction  strongly 
favored  the  adoption  of  the  reinforced  deck  and  buttress  form  of 
hollow  dam,  on  account  of  the  existence  of  an  experienced  con- 
struction organization  which  could  be  started  at  once  on  the  work 
and  push  it  to  completion  without  delay. 

The  materials  and  stresses  specified  for  use  in  this  design 
were  as  follows: 

Concrete — 

Deck  and  apron 1:2:4 

Buttresses 1:3:6 


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SCHREIBER  ON  ESTACADA  CONCRETE  DaM.  391 

Reinforcement — Corrugated  square  bars  50,000  lb.  elastic  limit  and  80,000 
to  100,000  lb.  ultimate  strength. 

Stresses — 

Modulus  of  elasticity  of  concrete 1,500,000  lb. 

Modulus  of  elasticity  of  steel 30,000,000  " 

Compressive  stress  in  concrete 500  lb.  per  sq.  in. 

Shear  in  concrete 75  "    " 

Tension  in  concrete 0  "    " 

Tension  in  reinforcement 15,000  "    " 

Base  pressures 100  "    " 

The  hollow  dam  of  the  design  selected  consists  of  a  series  of 
parallel  walls  or  buttresses  running  parallel  to  the  thread  of  the 


FIQ.   4. — SECTION  OP  DAM  THROUGH   SPILLWAY. 

stream,  with  an  upstream  covering  or  deck  on  one  side  and,  on 
the  spillway  section,  a  downstream  covering  or  apron  which  ter- 
minates at  its  base  in  a  heavy  curved  bucket  section  designed  to 
divert  and  discharge  the  falling  water  downstream  parallel  to  the 
river  bed.  A  section  of  the  dam  through  the  spillway  is  given  in 
Fig.  4,  and  through  the  intake  in  Fig.  5. 

The  deck,  which  is  inclined  45  deg.  with  the  vertical,  has  a 
thickness  that  varies  from  20  to  48  in.  depending  upon  the  depth. 
The  apron  which  makes  an  angle  of  30  deg.  with  the  vertical  also 
varies  in  thickness,  being  thickest  at  the  crest  and  bucket  but 
reduced  to  a  thickness  of  18  in.  on  the  straight  slope  section. 
The  reinforcement  in  deck  and  apron  is  laid  horizontally  2  in. 


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SCHREIBER  ON  EbTACADA  CONCRETE  DaM. 


from  the  under  side  of  the  slab  with  vertical  bars  on  24  in.  spac- 
ing as  an  extra  precaution  against  weakness  in  joints  and  to  avoid 
temperature  cracks.  Hydrated  lime,  30  lb.  per  cu.  yd.,  was  added 
to  the  deck,  crest  and  apron  to  make  the  material  less  pervious. 
The  extra  cost  for  this  material  averaged  23  cents  per  yd.  The 
buttresses  spaced  on  18  ft.  centers  are  built  in  horizontal  lifts  of 
12  ft.  and  vary  in  thickness  from  15  in.  at  the  top  to  38  in.  at  the 
bottom,  being  also  tapered  along  their  length  for  equalization  of 
pressure.     Haunches  with  18-in.  seats  for  the  deck  slabs  are  pro- 


FIG.   5. — SECTION  OF  DAM  THROUGH  INTAKE. 

vided  at  the  upstream  end  and  tongues  extended  between  the 
slabs  support  the  deck  forms  during  construction  and  provide  an 
opportunity  to  get  a  tight  joint  between  the  slab  and  the  buttress. 
Because  of  the  uncertain  character  of  the  foimdations  the  foot- 
ings were  spread  to  reduce  the  base  pressure  to  100  lb.  per  sq.  in. 
Additional  reinforcement  was  also  provided  in  the  bottom  lift 
to  permit  bridging  any  spaces  of  uncertain  bearing  value.  The 
spillway  section  of  the  dam  has  a  maximum  height  of  about  86  ft. 
and  the  bulkhead  section  a  maximum  height  of  about  101  ft. 


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SCHREIBER  ON  ESTACADA  CONCRETE  DaM. 


393 


As  constructed  at  Estacada  the  usual  features  were  embodied 
in  the  spillway  construction  with  the  addition  of  sluice  gates  and 
the  usual  closing  device  in  the  left  or  main  river  channel.  The 
spillway  end  abutment  was  of  solid  retaining  wall  section,  a  large 
part  of  it  being  built  in  gravel  and  clay,  serving  principally  as  a 
cut-off  or  core  wall  to  prevent  wash  around  the  end  of  the  dam. 
The  right-hand  or  bulkhead  end  abutment  was  considerably 
longer,  of  reinforced  retaining  wall  design. 

The  island  which,  as  stated,  was  included  in  the  development 


iL^jUt&W.J 


Fia.    6. — METHOD   OF   CONSTRUCTION   AND   FORM   WORK. 

was  found  to  be  of  such  poor  material  that  about  one-third  of  it 
was  entirely  removed  to  better  bottom  about  10  ft.  above  the 
water  surface  and  the  balance  was  notched  out  parallel  to  the 
deck  and  faced  with  2  ft.  of  concrete  which  formed  an  extension 
of  the  deck  and  tied  in  with  the  cut-off  wall  at  the  base  and  a 
low  section  of  dam  on  the  top  of  this  portion  of  the  island. 

The  total  length  of  the  spillway  or  overflow  section  extending 
from  the  left  abutment  to  the  non-overflow  section  on  the  island 
is  404  ft.  10  in.  and  has  a  rounded  crest  and  heavy  bucket  and 


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SCHREIBER  ON  ESTACADA  CONCRETE   DaM. 


apron  extending  over  the  downstream  side  of  the  island  far 
enough  to  fully  protect  this  portion  of  the  structure  from  imder- 
mining.  The  buttresses  in  this  portion  are  pierced  near  the  top 
with  openings  used  for  a  runway  extending  entirely  through  the 
dam  from  the  power  house  up  through  the  left  abutment. 

The  non-overflow  or  bulkhead  section  in  which  the  but- 
tresses extend  15  ft.  higher  and  are  covered  only  on  the  upstream 
side  and  top,  is  open  on  the  downstream  side.     One  bay  in  this 


FIG.  7. — METHOD  OF  CONSTRUCTION  AND  FORM  WORK. 

section  contains  a  large  concrete  fishway  tank  discharging  into  a 
concrete  fishway. 

Figs.  6  and  7  show  the  dam  in  course  of  construction  and  the 
various  types  of  forms  are  illustrated  in  Figs.  8,  9  and  10. 

Because  of  the  necessity  of  providing  adequate  trash  rack 
area,  supporting  penstocks  and  meeting  the  requirements  imposed 
by  the  high  tension  transformers  and  wiring  installed  here,  the 
power-house  section  of  the  dam  is  quite  complicated  and  required 
considerable  thought  and  skill  to  work  out  the  situation  satisfac- 
torily. 


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SCHREIBEB  ON  EsTACADA  CONCRETE  DaM. 


395 


To  locate  the  penstocks  at  convenient  distances  and  properly 
support  them  on  the  adjoining  buttresses  as  they  pass  from  the 
intakes  through  the  dam  to  the  turbines,  the  spacing  between 
buttresses  is  here  made  14  ft.  instead  of  18  ft.  as  in  the  balance 
of  the  construction.  An  extra  thickness  of  deck  with  additional 
reinforcement  is  provided  aroimd  the  penstock  intakes  and  to 
carry  the  weight  and  prevent  vibration  several  extra  heavy 
struts  are  built  against  each  penstock  so  as  to  tie  across  to  the 
adjoining  buttresses. 

To  provide  means  for  getting  machinery  into  the  power 
house,  which  is  built  against  the  downstream  ends  of  the  but- 
tresses  of   the    power-house   section,   a    railway   connection    is 


«1 

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FIG.   8. — ^METHOD   OF  HOLDING   TONGUE    AND   HAUNCH    FORMS  IN   PLACE. 

extended  along  the  top  of  the  right  end  abutment  so  as  to  enter 
directly  on  the  unloading  platform  where  crane  service  is  avail- 
able to  quickly  lower  material  to  the  power-house  floor  level  and 
where,  after  being  transferred  by  a  suitable  truck,  it  is  handled 
by  the  power-house  crane. 

The  deck  for  the  intake  section  of  the  dam  is  set  back  from 
the  face  of  the  deck  below  it  to  allow  space  behind  the  trash 
racks  for  head  gates  and  stop  logs  and  to  permit  easy  access  of 
the  water  from  racks  to  penstock  opening  and  is  of  special  con- 
struction on  this  account. 

The  racks,  hoists  and  loading  platform  are  housed  by  a  con- 
crete structure  extending  the  full  length  of  the  power  house.    The 


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SCHREIBER  ON  EsTACADA  CONCRETE  DaM. 


power  house  has  a  solid  concrete  substructure  with  flood  protec- 
tion for  a  height  of  14  ft.  above  which  is  a  concrete  and  steel 
superstructure. 

The  initial  installation  consists  of  three  6000  h.p.  240  r.j).m. 
twin  flumC;  center  discharge,  volute  casing  turbines,  of  special 
design  originally  suggested  by  us,  each  connected  to  a  3300  k.w., 
3-phase,  10,000-volt  generator,  and  penstock  and  power-house 
space  is  provided  for  fwo.  more  units. 

These  turbines  feed  from  below  through  a  cast  iron  Y  pipe 
connection  to  their  penstocks,  have  substantial  cast  iron  bed 
plates  and  casings,  presenting  a  neat  and  compact  appearance. 


m 


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a^  *.  io»  ftevin 


FIG.   9. — METHOD   OF   ANCHORING   DECK   SLAB    FORMS. 

The  oil  type  governors  are  provided  with  the  usual  distant  control 
and  other  auxiliaries  as  well  as  extra  flyball  head  for  emergency 
"shut  downs"  in  case  the  regular  head  fails  to  act. 

The  generators  are  so  supported  on  the  foimdations  as  to 
have  ample  ventilation  in  all  parts.  A  direct  connected  exciter 
on  the  outboard  end  of  each  shaft  and  one  reserve  combined 
turbine  and  motor-driven  exciter  provide  the  necessary  exciting 
current. 

The  3-phase,  60-cycle,  33,000-volt  delta  and  57,000-volt  Y 
step-up  transformers,  each  carrying  the  load  of  the  adjacent 
generator,  are  located  in  the  dam  back  of  the  turbines  and  inmae- 


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SCHREIBER  ON  ESTACADA  CONCRETE  DaM. 


397 


diately  above  them  are  the  57,000-volt  high  tension  and  the 
10,000-volt  low  tension  oil  switches,  bus  bars,  electrolytic  light- 
ning arresters,  etc.,  connecting  with  the  two  3-phafie  transmission 
lines  to  Portland. 


CONSTRUCTION. 


The  scarcity  of  suitable  construction  materials  was  at  fii^t  a 
matter  of  considerable  importance  but  with  the  assistance  of 
Mr.  Robert  S.  Edwards,  consulting  chemical  engineer,  of  Port- 
land, who  was  retained  to  investigate  the  quality  and  costs  of 


s 


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flMM  dott*«  an  MM  to  np- 

•ort  ToacM  roiw  oBtll  boia 

(7  Belt*.    BmovM  UUt*  ft»apr«t«iv 


■ttHhtiw  teok  Strei   ' 
*•  »  4-  «  4-  VMtar 


1-  ■  I"  h»U  ta  CtnanU  ter 
4ptk-4,  iB«  VMf  to  ioppoit 


FIG.    10. — FORMS   FOR   BUTTRESS. 

sand,  stone  and  cement  available,  satisfactory  materials  were 
obtained. 

Sand  for  construction  in  this  section  is  ordinarily  pumped 
from  the  Columbia  River,  but  on  investigation  of  the  possibilities 
along  the  railway  right  of  way  a  large  pit  was  discovered  which 
provided  suflScient  sand  and  gravel  of  good  quality  at  consid- 
erable saving  for  not  only  this  job  but  for  much  of  the  other 
construction  work  which  the  company  had  on  hand. 

The  only  rock  quarry  opened  up  was  also  along  the  railway 
right  of  way,  and  though  far  from  satisfactory  produced  a  good 
quality  of  basalt  rock  at  reasonable  cost. 


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398  SCHREIBER  ON  ESTACADA  CONCRETE  DaM. 

Because  of  the  fact  that  the  cement  manufacturing  business 
on  the  Pacific  Coast  was  still  in  a  rather  non-«ystematized  state 
both  as  regards  the  standard  of  uniform  quality  and  the  matter 
of  regular  supply,  the  purchase  of  cement  was  considered  only 
after  a  careful  personal  investigation  and  report  on  the  available 
mills  on  the  coast  to  determine  the  history  and  quality  of  the 
product  and  the  probability  of  securing  satisfactory  shipments. 
Considerable  time  and  expense  were  devoted  to  this  investigation, 
but  with  these  data  in  hand  an  advantageous  contract  based  on 
satisfactory  specifications  was  closed  for  sufi^cient  cement  to  meet 
the  company's  requirements  for  several  years  at  a  considerable 
saving. 

The  time  for  construction  being  quite  limited  with  a  large 
amoimt  of  excavation  to  be  made,  the  construction  plant  invest- 
ment was  considerable.  The  equipment  for  excavation  consisted 
of  8  steam  drills  assisted  by  5  derricks,  1  elipctric  locomotive  and  a 
steam  locomotive  crane.  For  the  core  drilling  and  grouting  there 
were  required  6  Davis-Calyx  core  drills,  pressure  tanks  for  water 
testing  and  2  motor-driven  Peerless  air  compressors  and  2  Canniff 
air-stirring  tanks  for  grout  supply. 

The  sand  pit  was  equipped  with  screen  for  eliminating  the 
large  stone  and  coarse  gravel  and  with  several  bins  which  were 
arranged  to  empty  directly  into  the  railway  cars  which  passed 
beneath  them.  The  quarry  equipment  included  a  motor-driven 
crusher  and  screens  together  with  bins  for  dumping  directly  into 
the  cars.  At  the  site  liberal  sand  and  stone  bins  were  provided 
for  each  of  the  2  electrically  driven  1-yd.  mixers  first  installed. 
A  third  steam-driven  mixer  was  later  installed  and  the  three 
together  were  utilized  to  supply  the  two  cableways  which  carried 
the  concrete  directly  onto  the  work. 

Cement  and  lime  storage  sheds  were  also  provided  close  to 
the  mixers  to  meet  the  ordinary  needs  between  receipt  of  ship- 
ments. 

The  concrete  mixing  plant  and  material  storage  bins  and 
sheds  were  located  beyond  the  right  end  of  the  dam  where  they 
were  fed  by  electric  railway  supply  trains  from  the  company's 
line  to  Cazadero.  The  mixed  concrete  was  then  fed  to  the  cable- 
way  buckets  for  distribution  over  the  work.  On  the  buttress 
forms  tracks  were  arranged  to  carry  a  suitable  concrete  car  which 


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SCHREIBEB  ON  ESTACADA  CONCRETE   DaM.  399 

received  the  concrete  from  the  cableway  bucket  and  distributed 
it  as  required  in  the  buttress. 

The  construction  necessarily  proceeded  along  lines  dictated 
to  a  considerable  extent  by  the  large  excavation  necessary  on  the 
island  and  the  time  required  for  installation  of  machinery  in  the 
power  house. 

Starting  on  the  left  channel  during  the  beginning  of  the  dry 
season  the  cut-off  wall  was  installed,  holes  drilled  and  grouted 
and  the  first  lift  of  a  buttress  constructed  in  midstream  to  serve 
in  dividing  this  channel  during  the  following  dry  season  when 
completing  the  construction.  During  this  time  excavation  and 
grouting  were  proceeding  on  the  left  bank  and  island  above  water 
line  to  permit  concreting  at  these  points  to  follow  as  soon  as 
possible.  Next  the  right  or  power-house  channel  was  per- 
manently unwatered  and  the  old  river  chasm  found  below  the 
bed  of  the  stream  was  cleaned  out  and  work  was  pushed,  on  grout- 
ing and  concreting  to  permit  installation  of  racks,  penstocks  and 
machinery  in  advance  of  the  completion  of  the  spillway.  The 
great  amoimt  of  excavation  on  the  island  hindered  this  portion  of 
the  work  to  some  extent,  but  fortunately  no  unusual  floods  were 
experienced  and  the  entire  structure  up  to  the  left  river  channel 
was  completed  early  enough  so  that  with  the  installation  of  two 
special  openings  in  addition  to  the  four  sluice  gates  the  stream 
flow  could  be  passed  imtil  such  time  as  it  might  be  possible  to 
discharge  it  over  the  crest. 

The  construction  work  started  in  June,  1910,  and  the  water 
first  passed  over  the  spillway  November  7,  1911,  which  in  view 
of  the  conditions  to  be  met  may  well  be  considered  quite  rapid 
construction.  The  lar£:?st  average  force  employed  for  any  month 
was  655  men.  The  record  excavation  was  9476  cu.  yd.  per 
month.  The  greatest  yardage  of  concrete  placed  any  month  was 
8325  cu.  yds. 

Credit  is  due  Mr.  Robert  S.  Edwards,  who  had  charge  of  the 
cement  investigations  and  testing,  and  Mr.  Frank  R.  Fisher, 
resident  engineer  on  the  later  part  of  the  construction,  for  data 
used  in  this  paper. 


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UNIT  COSTS  OF  REINFORCED  CONCRETE 
FOR  INDUSTRIAL  BUILDINGS. 

By  Chester  S.  Allen.* 

Unit  costs  are  harmless  when  used  with  judgment  and 
prudence,  but  likely  to  bring  remorse  and  anguish  when  employed 
promiscuously.  Rare  and  talented  indeed  is  the  man  who  pos- 
sesses the  experience,  judgment  and  intuitive  sense  to  know 
when,  where  and  how  to  properly  modify  any  tables  or  state- 
ments of  unit  costs  to  meet  the  peculiar  conditions  of  each  indi- 
vidual case.  While  the  figures  given  in  this  paper  are  all  taken 
from  structures  erected  during  the  past  two  years  under  the 
writer's  supervision,  the  wide  range  of  territory,  local  condi- 
tions, and  different  seasons  of  the  year  imder  which  the  various 
pieces  of  work  have  been  executed  are  so  great  as  to  render  the 
information  of  value  only  in  a  very  general  way. 

As  a  general  proposition  it  has  been  found  that  reinforced 
concrete  is  the  lowest-priced  fireproof  material  suitable  for  fac- 
tory construction  and  while  it  is  true  that  its  first  cost  will  gen- 
erally run  from  5 -to  20  per  cent  higher  than  first-class  mill  con- 
struction, recently  in  several  instances,  with  lumber  at  a  high 
price,  reinforced  concrete  has  worked  out  cheaper  than  brick  and 
timber.  It  is  especially  adapted  to  heavy  construction  and  for 
heavy  loads  of  200  lb.  per  sq.  ft.  and  over  where  the  spans  are 
18  to  20  ft.  centers,  not  even  timber  can  compete  with  it. 

The  unit  costs  of  projected  or  completed  buildings  are  com- 
monly figured  either  as  so  much  per  cubic  foot  or  as  so  much 
per  square  foot  of  area  occupied.  Table  I  gives  the  unit  costs 
both  on  the  sq.  ft.  and  the  cu.  ft.  basis,  together  with  a  general 
description  of  a  number  of  reinforced  concrete  industrial  buildings 
of  different  types  erected  during  the  past  two  years.  It  will  be 
seen  from  an  examination  of  this  table  that  the  average  cost  per 
sq.  ft.  of  these  buildings,  excluding  the  one-story  structures,  was 
$1.12;  while  the  average  cost  per  cu.  ft.  was  8.7  cts.  The  one- 
story  structures   both   had   reinforced   concrete   sawtooth   roofs 

*■  Engineer,  Lockwood,  Greene  &  Company,  Boston,  Mass. 

(400) 


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Allen  on  Unit  Costs  op  Reinforced  Concrete.       401 


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402       Allen  on  Unit  Costs  of  Reinforced  Concrete. 

and  the  average  cost  per  sq.  ft.  was  $1.77,  while  8.5  cts.  was  the 
average  cost  per  cu.  ft.  The  above  costs  are  for  the  finished 
buildings,  including  plumbing,  but  do  not  embody  heating,  light- 
ing, elevators,  sprinklers  and  power  equipment.  The  cost  per 
sq.  ft.  of  floor  area  was  obtained  by  dividing  the  cost  of  the 
building  by  the  total  number  of  sq.  ft.  of  floor  area  exclusive 
of  roof  area  but  including  basement  floors;  and  the  cost  per  cu. 
ft.,  by  dividing  the  cubical  contents  into  the  cost  of  the  structxire. 

While  no  coal  pockets  are  included  in  Table  I,  it  has  been 
our  experience  that  above  3000  tons  capacity  reinforced  concrete 
elevator  coal  pockets  cost  from  $5.50  to  $7.50  per  ton  of  capacity. 
Standpipes,  exclusive  of  the  foundations,  average  from  2^  to  3  cts. 
per  gallon  of  capacity. 

On  much  of  the  reinforced  concrete  work  which  has  been 
done  imder  our  supervision  it  has  been  possible,  owing  to  the 
contract  being  either  on  a  percentage  or  cost  plus  a  fixed  sum 
basis,  to  obtain  quite  accurate  and  comprehensive  cost  data. 
This  data,  of  course,  is  only  of  particular  value  when  all  the 
local  color  of  each  specific  case  is  known,  but  the  average  results 
are  at  least  interesting. 

The  average  unit  cost  of  the  1-2-4  concrete  in  the  floors 
including  the  beams,  girders  and  slabs,  was  $6.10  per  cu.  >d., 
and  for  the  columns  $6.70  per  cu.  yd.  Where  1-1^-3  mixture 
was  used  for  the  columns  the  average  cost  was  $7.60  per  cu.  yd. 
This  cost  was  made  up  of  the  items  of  cement,  sand,  stone  or 
gravel,  labor  and  plant.  The  cement  of  course  varied  greatly 
with  the  demand,  but  the  average  net  cost  was  $1.35  per  barrel 
including  3  cts.  for  tests.  The  sand  averaged  80  cts.  per 
cu.  yd.  and  the  crushed  stone  $1.25  per  cu.  yd.  The  cost  of 
labor  of  unloading  the  materials  and  mixing  and  placing  the 
concrete  varied  from  65  cts.  to  $2.90  per  cu.  yd.  The  cost  of 
plant,  consisting  of  freight,  depreciation  or  rental  of  mixing  and 
hoisting  towers,  erection  of  same,  power  and  coal,  and  losses 
and  waste  on  the  small  tools,  ranged  from  50  cts.  to  $1.50  per 
cu.  yd.  of  concrete  placed. 

Next  to  the  proper  design  of  the  structural  features  of  a 
concrete  building,  the  economical  design  of  the  form  work  is  of 
paramoimt  importance.  The  truth  of  this  statement  is  borne 
out  by  the  fact  that  on  the  average  job  the  cost  of  the  forms 


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Allen  on  Unit  Costs  of  Reinforced  Concrete.       403 

amounts  to  about  one-third  the  cost  of  the  entire  structure.  On 
the  buildings  under  consideration  the  average  cost  of  the  forms 
for  the  floors,  including  beams,  girders  and  slabs,  was  10  cts. 
per  sq.  ft.,  and  for  the  columns  13  cts.  per  sq.  ft.  The  lowest 
cost  was  in  a  building  of  the  girderless  or  flat  slab  type  of  con- 
struction, where  by  the  intelligent  use  of  corrugated  iron  for 
the  slab  forms  the  cost  of  the  floor  forms,  including  wall  beams, 
was  7  cts.  per  sq.  ft.  The  highest  cost  was  for  an  artistic  but 
not  elaborate  overhanging  cornice  on  a  12-story  building,  and 
was  32  cts.  per  sq.  ft.  This  last  item  rather  forcibly  demon- 
strates that  any  attempt  at  architectural  development  is  very 
apt  to  be  a  costly  proposition. 

The  cost  of  the  labor  of  making,  erecting  and  stripping  the 
forms  varied  according  to  the  price  of  lumber,  design  of  the 
structure,  method  of  forming,  character  of  the  supervision  and 
the  skill  of  the  workmen  from  4J  to  12  cts.  per  sq.  ft.  The  cost 
of  lumber,  nails  and  oil  divided  by  the  sq.  ft.  of  forms 
averaged  from  2J  to  ^  cts.  per  sq.  ft. 

The  cost  of  bending  and  placing  the  reinforcing  metal,  in- 
cluding the  necessary  wire,  averages  $10  per  ton,  the  range  being 
from  $5.75  to  $17.20  per  ton. 

Granolithic  floor  finish  l}-in.  thick  when  laid  before  the 
concrete  below  it  had  set  so  as  to  form  one  homogeneous  slab, 
cost  on  the  average  of  4^  cts.  per  sq.  ft.  When  put  on  after  the 
rough  concrete  slab,  the  cost  averaged  7  cts.  per  sq.  ft. 

Inasmuch  as  the  only  economical  design  of  a  reinforced 
concrete  structure  is  one  which  closely  resembles  that  of  the 
steel  skeleton  type,  the  relative  cost  of  the  various  materials 
commonly  used  for  curtain  walls  under  the  windows  may  be  of 
interest.  The  writer  has  used  brick,  vitrified  tile,  concrete  blocks, 
cast  concrete  slabs  and  solid  concrete  walls  for  this  purpose. 

The  most  common  type  of  curtain  wall  has  been  either  an 
8-in.  or  12-in.  brick  wall  resting  on  the  concrete  wall  beam.  The 
average  cost  of  these  walls  has  been  45  cts.  per  sq.  ft.  There 
is  practically  no  difference  in  cost  between  the  8-in.  and  the 
12-in.  brick  curtain  wall,  as  the  saving  in  material  is  offset  by 
the  great  amount  of  extra  labor  in  culling  and  laying  the  thinner 
wall. 

An  excellent  and  inexpensive  curtain  wall  is  constructed 


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404      All^n  on  Unit  Costs  op  Reinforced  Concrete. 

by  using  8  x  12  x  18  in.  vitrified  tile.  This  is  a  non-absorbent 
wall  and  when  properly  laid  in  cement  mortar  makes  a  tight 
weather-proof  curtain  wall.  The  cost  of  this  wall  averages  about 
25  cts.  per  sq.  ft.  If  the  tile  is  plastered  both  sides,  the  cost  is 
about  38  cts.  per  sq.  ft. 

Where  8-in.  concrete  curtain  walls  were  cast  in  place  after 
the  skeleton  frame  was  completed,  the  average  cost  was  40  cts. 
per  sq.  ft.,  and  when  poured  simultaneously  with  the  columns 
48  cts.  per  sq.  ft.  4-in.  cast  concrete  slabs  cost  about  35  cts. 
per  sq.  ft. 

While  concrete  blocks  make  a  very  cheap  and  light  curtain 
wall,  the  price  being  about  the  same  as  for  the  8-in.  tile,  the 
writer's  experience  with  them  has  been  rather  unfortunate  on 
account  of  the  extreme  porosity  of  the  blocks  used. 

Where  the  location  of  the  buildings  has  demanded  special 
treatment  of  the  exposed  surfaces,  they  have  generally  been 
specified  to  be  rubbed  with  a  block  of  carborundum.  The  aver- 
age cost  of  this  work  has  been  4  cts.  per  sq.  ft.  In  two  instances 
portions  of  the  structures  have  been  bush  hammered  with  a  result- 
ing average  cost  of  7  cts.  per  sq.  ft. 

Concrete  piles  were  used  on  the  foundations  of  several  of 
the  buildings  and  the  average  cost  of  the  piles  was  $1.15  per 
lin.  ft. 

The  most  common  methods  of  waterproofing  concrete  struc- 
tures are  by  the  introduction  of  foreign  ingredients  into  the  con- 
crete, by  the  application  of  a  compound  to  the  concrete  surface, 
by  the  use  of  paper  or  felt  waterproofing,  and  by  accurately 
grading  and  proportioning  the  aggregates  and  the  cement. 

Where  an  addition  of  hydrated  lime  in  the  proportions  of 
10  per  cent  to  the  weight  of  the  cement  has  been  used,  the  added 
cost  to  a  cubic  yard  of  1-2-4  concrete  has  been  50  cts.  Patented 
compoimds  have  cost  from  25  to  35  cts.  per  sq.  ft.  of  surface 
covered.  On  horizontal  or  inclined  surfaces,  we  have  sometimes 
used  a  granolithic  surface  of  rich  mortar  of  Portland  cement  and 
sand  or  Portland  cement  and  screenings  in  the  proportions  of 
1-1,  laid  at  the  same  time  as  the  base  and  troweled  as  in  side- 
walk construction.  The  cost  of  this  work  has  been  about  5  cts. 
per  sq.  ft. 

Taken  as  a  whole,  the  lowest  possible  cost  on  a  reinforced 


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Allen  on  Unit  Costs  of  Reinforced  Concrete.      405 

concrete  building  can  be  obtained  only  by  a  careful  study  of 
each  particular  case  to  determine  the  cheapest  type  of  construc- 
tion and  most  economical  spacing  of  columns.  As  a  general 
proposition  it  has  been  found  that  for  light  loads  with  ordinary 
beam  and  girder  construction  the  most  economical  spacing  of 
columns  is  18  ft.  each  way  and  for  flat  slab  construction  20  ft. 
each  way.  For  heavy  loads  such  as  300  lb.  per  sq.  ft.  and  over, 
it  has  been  our  experience  that  the  cheapest  colimm  spacing  for 
beam  and  girder  construction  is  15  ft.  by  15  ft.,  and  for  flat  slab 
construction  17  ft.  by  17  ft.  In  arriving  at  the  most  economical 
layout  it  is  always  well  to  bear  in  mind  that  the  construction 
which  allows  the  greatest  simplicity  of  form  units,  together  with 
the  maximum  number  of  repetitions  of  same,  is  invariably  the 
one  that  will  work  out  cheapest  in  the  end.  The  fact  that  the 
actual  amoimt  of  concrete  or  reinforcement  required  for  a  certain 
floor  construction  is  less  than  that  required  in  another  by  no 
means  implies  that  this  is  actually  the  cheapest  floor  construc- 
tion, as  the  unit  labor  of  the  form  work  may  easily  have  been 
increased  out  of  all  proportion. 


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REINFORCED  CONCJRETE  CONVENTION  HALL  AT 
BRESLAU,  GERMANY.* 

By  Dr.  S.  J.  TRAUER.f 

There  is  being  built  at  the  present  time  in  the  City  of 
Breslau,  Germany,  a  large  convention  and  exhibition  hall  (Fig.  1), 
surmounted  by  the  largest  concrete  dome  in  the  world.  The 
building,  of  reinforced  concrete  throughout,  has  a  seating  capacity 
of  9000  persons  and  standing  room  for  12,000  people. 

The  structure  (Fig.  2)   consists  essentially  of  a  main  hall, 


FIG.    1. — CONVENTION    HALL,    BRESLAU,    GERMANY. 

circular  in  form,  connecting  directly  with  four  semi-circular  halls 
called  Apsiden,  all  of  which  are  surrounded  by  a  lower  circular 
hall  serving  exhibition  purposes.  A  dome  of  213  ft.  span  with 
a  rise  of  65  ft.  rests  on  the  substructure,  65  ft.  in  height,  and 
carries  a  light  dome. 

The  substructure  (Fig.  3)  consists  of  four  main  arches,  (A) 
of  131  ft.  span  and  62  ft.  rise,  circular  in  plan  and  supported 
by  four  piers.  Each  main  arch  (^4)  is  supported  from  the  out- 
side by  four  auxiliary  arches   (B)  which  cover  a  smaller  semi- 


*  Translated  from  author's  notes  by  the  Secretary. 
fCity  Bridge  Engineer,  Breslau,  Germany. 

(406) 


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Traubr  on  Reinforced  Concrete  Convention  Hall.    407 

circular  hall  called  an  Apside.  These  auxiliary  arches  rest  on 
individual  piers  and  take  the  outward  thrust  from  the  main 
arches.  The  area  of  the  cross-section  of  the  main  arch  at  the 
skew-back  is  24  sq.  ft.  and  at  the  crown  3.6  sq.  ft.,  all  reinforced 
with  round  bars  of  1.18  in.  diameter.  The  main  arches  are  soUd 
and  are  subject  to  their  own  temperature  stresses  only.     The 


Smfi^'^^p. 


FIG.   2. — PLAN   OF   CONVENTION   HALL,   BRESLAU,    GERMANY. 

horizontal  thrust  amounts  to  771  tons,  the  pressure  at  the  skew- 
back  is  1323  tons  and  in  addition  the  main  arches  are  subjected 
to  torsion  and  bending. 

The  auxiliary  arches  (JS)  which  receive  about  220  tons  thrust 
from  the  main  arches,  are  connected  with  the  main  arches  and 
the  small  abutments  through  ball  bearings  (C)  of  malleable  steel 


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408   Trauer  on  Reinforced  Concrete  Convention  Hall. 

castings  so  that  the  auxiliary  arches  receive  only  axial  stress. 
These  arches  are  3.28  ft.  in  width  and  5.28  ft.  in  thickness. 

The  substructure  is  entirely  independent  of  the  dome  itself 
and  supports  the  latter  by  means  of  steel  roller  bearings  (D)  under 
each  rib,  the  bearings  having  radial  movement.  So  that  in 
general  only  vertical  stresses  are  transmitted  to  the  substructure, 
which  is,  therefore,  not  subject  to  the  temperature  stresses  in  the 
dome.     The  wind  pressure  on  the  dome  is  not  transmitted  in  a 


FIG.   3. — SECTION  THROUGH  MAIN   AXIS. 

radial  but  in  a  tangential  direction,  that  is,  the  direction  in  which 
the  four  main  arches  have  the  highest  power  of  resistance.  The 
frames  (E)  over  the  four  abutments  of  the  structures  are  calcu- 
lated to  take  up  the  total  wind  load  on  the  dome. 

The  dome  consists  of  32  half  ribs  (F),  which  bear  on  the 
top  against  the  pressure  ring  ((?)  and  on  the  bottom  against  the 
tension  rmg  (H).  The  pressure  ring  of  47.2  ft.  inside  diameter 
is  surmoimted  by  an  upper  light  dome  (•/)•  The  pressure  ring 
with  a  cross-sectional  area  of  19.7  sq.  ft.  carries  551  tons  in  com- 


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Trauer  on  Reinforced  Concrete  Convention  Hall.  409 


FIG.  4. — RIVETED  STEEL  TENSION  RING  AND  HAUNCH  OF  ONE  RIB. 


FIG.    5. — SUBSTRUCTURE     AND    CENTERING     FOR    HALF-RIBS    OF    DOM£. 


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410   Trauer  on  Reinforced  Concrete  Convention  Hall. 


FI.J.    (). — CONCRETING    HALF-RIBS   OF   DOME. 


^''«'IIJIil iillllMII'tt'»^"'    - 


FIG.    7. — VIEW   OF   INTERIOR. 


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Trauer  on  Reinforced  Concrete  Convention  Hall.    411 

pression  and  the  tension  ring  (Fig.  4),  with  a  cross-sectional  area 
of  29.9  sq.  ft.,  carries  551  tons  in  tension.  The  ribs  carry  a  hori- 
zontal thrust  of  110  tons  and  115  tons  on  the  skew-back  and 
have  a  cross-sectional  area  which  increases  from  3.4  ft.  x  2.13 
ft.  to  3.94  ft.  X  2.62  ft.  The  ribs  and  the  tension  and  pressure 
rings  are  reinforced  with  round  rods.  The  ribs  are  strengthened 
by  means  of  rings  (M)  and  horizontal  circular  slabs  (K).  The 
tension  ring  is  of  riveted  steel  construction. 

The  roof  supports  are  almost  horizontal,  the  windows  (M) 
are  vertical  so  that  in  the  case  of  snow  the  interior  illumination 
will  not  be  affected. 

The  architectural  design  was  made  by  the  City  Building 
Engineer,  Berg;  the  calculations  by  the  City  Bridge  Engineer, 
Dr.  Trauer,  and  the  verification  and  construction  by  the  firm 
of  Dyckerhoff  &  Widmann,  of  Dresden,  Germany. 


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THE  SUITABILITY  OF  CONCRETE  FOR  GAS  HOLDER 

TANKS. 

By  Herbert  W.  Alrich.* 

In  its  purpose  the  gas  holder  represents  the  common  feature 
of  all  manufacturing  enterprises — ^it  is  the  receptacle  for  the 
storage  of  the  product.  But  in  their  design,  gas  holders  are  not 
resembled  by  any  structure  or  equipment  employed  in  any  other 
line  of  industry.  A  prominent  engineering  writer  has  recently 
said  that  the  modem  gas  holder  is  ''A  magnificent  achievement 
in  engineering,  and  one  of  the  wonders  of  it  is  the  telescopic 
feature."  As  the  majority  of  engineers  are  not  familiar  with 
the  mechanical  features  of  a  gas  holder,  a  description  is  given; 
for  in  discussing  tank  design,  it  is  necessary  to  consider  the 
structure  as  a  whole. 

There  are  three  principle  parts  to  a  gas  holder;  the  tank, 
the  telescopic  sections  or  gas  holder  proper,  and  the  guide  frame. 
Each  of  these  parts  differs  from  the  others  in  function  and  in 
the  type  of  construction.  The  tank,  resting  upon  the  ground, 
is  filled  with  water  up  to  a  level  about  15  in.  below  the  top.  The 
gas  holder  proper  consists  of  the  telescopic  sections,  of  which 
there  are  five  in  the  case  of  the  largest  holders  that  have  been 
built  in  this  country.  These  sections  consist  of  cylindrical  steel 
shells,  concentrically  located  with  relation  to  each  other  and  to 
the  tank.  When  the  holder  contains  no  gas,  these  shells  are 
nested  together,  resting  upon  the  bottom  of  the  tank  and  sub- 
merged almost  completely  in  the  water  which  the  tank  contains. 
(See  Fig.  L)  The  outer-most  shell  is  usually  about  3  ft.  less 
in  diameter  than  the  tank,  and  each  succeeding  section  is  about 
2  ft.  9  in.  less  in  diameter  than  the  preceding  one.  All  of  the 
sections  are  open  at  each  end,  with  the  exception  of  the  inner- 
most one,  the  upper  end  of  which  is  enclosed  by  crown  plating, 
having  a  spherical  form. 

The  inlet  and  outlet  pipe  connections  enter  the  tank  through 


*  Engineers'  Department.  Coneolidated  Gas  Company  of  New  York. 

(412) 


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Alrich  on  Concrete''for  Gas  Holder  Tanks. 


413 


the  bottom  and  pass  vertically  upward  through  the  water  and 
termmate  at  an  elevation  above  the  water  and  just  under  the 
crown  of  the  inner  section.  When  gas  is  admitted  to  the  holder, 
it  first  acts  upon  the  crown,  lifting  that  section  gradually  out  of 
the  water  as  shown  by  Fig.  2,  until  the  cup,  constructed  around 
the  lower  edge  of  that  shell,  engages  the  upper  edge  of  the  next 


FIG.    1. — CROSS  SECTION  OF  A   GAS   HOLDER  GROUNDED. 

outside  section.  To  accomplish  this  engagement,  the  upper  edge 
of  each  outer  section  is  constructed  in  the  form  of  a  continuous 
annular  hook,  called  the  grip,  and  correspondingly  the  lower 
edge  of  each  section,  except  the  outermost  one  is  formed  into  a 
continuous  annular  cup.  Both  the  grip  and  the  cup  are  identical 
in  construction,  and  differ  only  in  the  respect  that  the  grip  is 
inverted  to  permit  interlocking  with  the  cup  as  shown  by  Fig.  3. 


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414        Alrich  on  Concrete  for  Gas  Holder  Tanks. 

As  the  inflation  of  the  holder  continues,  each  succeeding  section 
is  lifted  out  of  the  water,  and,  in  turn,  picks  up  the  next  outer 
section.  As  each  interlocked  cup  and  grip  pass  upward  out  of 
the  tank,  there  is  carried  along  that  quantity  of  water  which  is 
necessary  for  forming  a  hydraulic  seal  against  the  maximum 


FIG.    2. — HOLDER   PROPER   JUST   BEFORE    ENQAQINO    AN   ADDITIONAL   SECTION. 

pressure  of  the  holder.     This  action  continues  until  the  holder 
is  filled  to  the  limit  of  its  capacity  as  shown  by  Fig.  4. 

While  thus  ascending,  or  conversely  descending,  the  sec- 
tions are  maintained  in  their  relative  concentric  positions  by 
two  sets  of  rollers.  First,  the  rollers  spaced  equi-distant  around 
the  lower  edges  of  the  shells,  and  second,  the  rollers  mounted 
on  brackets  attached  to  the  upper  edges  of  the  shells.     The  first 


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Alrich  on  Concrete  for  Gas  Holder  Tanks.        415 


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416        Alrich  on  Concrete  for  Gas  Holder  Tanks. 

set  are  known  as  the  internal  rollers,  and  travel  upon  vertical 
guides,  located  on  the  inner  surface  of  the  tank  and  also  on  the 
inner  siurface  of  each  shell,  except  that  of  the  innermost  section. 
The  other  set  of  rollers  travel  upon  the  guide  rails,  which  are 
carried  by  the  guide  frame.  The  guide  frame  consists  of  vertical 
columns  spaced  equi-distant,  and  about  30  ft.  apart  around  the 


FIG.   4. — HOLDER  FULLY  INFLATED. 

circumference  of  the  tank.  These  columns  are  connected  by 
horizontal  and  diagonal  cross  bracing.  The  frame  is  carried  to 
such  a  height  as  will  provide  guidance  for  the  inner  section  in 
its  maximum  upward  travel.  It  will  be  apparent  from  this  dis- 
cussion that  the  enormous  pressure  of  the  wind  against  the  inflated 
sections  is  ultimately  transmitted  to  the  guide  frame  by  the  tank. 


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Alrich  on  Concrete  for  Gas  Holder  Tanks.       417 

In  the  selection  of  materials  in  manufacturing,  we  are  sub- 
ject to  an  inexorable  law  of  suitability.  In  producing  any  manu- 
facture, there  will  be  ultimately  employed  that  material  which 
possesses  preponderant  advantage.  The  use  of  any  other  cannot 
long  be  sustained.  From  the  very  beginning  of  the  gas  industry, 
100  years  ago,  the  guide  frames  and  holder  sections  have  been 
built  exclusively  of  iron  or  steel.  It  does  not  appear  that  any 
attempt  was  ever  made  to  use  any  other  materials.  In  the  con- 
struction of  the  tanks,  however,  many  different  materials  and 
combinations  of  materials  have  been  employed.  It  is  true,  how- 
ever, that  in  this  country,  until  recent  years,  all  holder  tanks 
were  built  either  of  brick  or  stone;  but  in  England,  the  birthplace 
of  the  gas  industry,  there  were  constructed  tanks  of  almost  every 
conceivable  type,  many  of  the  designs  being  more  fanciful  than 
practical.  It  was  inevitable  that  those  constructions  without 
merit  should  disappear  until  the  prevailing  practice,  throughout 
the  world,  during  the  last  twenty  years,  may  be  stated  as  limited 
to  steel  tanks  placed  upon  the  ground,  and  brick  or  concrete 
tanks  located  below  the  ground.  During  the  last  ten  years  the 
preponderance  of  advantage  in  this  country  has  been  in  favor  of 
steel  tanks  for  all  holders,  large  or  small.  In  England,  though 
concrete  tanks  had  been  constructed  as  far  back  as  the  year  1870, 
the  practice  of  the  last  decade  has  been  quite  imiformly  to  build 
small  tanks  of  steel,  and  large  tanks  of  brick,  there  being  but  few 
instances  of  concrete  construction.  In  Continental  Europe, 
practice  for  a  decade  has  followed  the  English,  with  the  excep- 
tion that  during  the  last  three  or  four  years  there  has  been  a 
marked  tendency  toward  the  exclusive  employment  of  steel, 
though  a  few  concrete  tanks  of  small  size  have  also  been  con- 
structed. 

The  competitive,  economic  and  geological  conditions  exist- 
ing in  England,  all  favor  the  brick  tank  for  large  holders.  While 
the  population  of  the  Island  of  Great  Britain  is  somewhat  less 
than  that  of  the  United  States,  the  number  of  concerns  engaged 
in  holder  construction  is  very  much  greater,  in  fact  the  building 
of  the  largest  holders  in  this  country  is  confined  to  a  very  few 
companies,  having  special  qualifications  and  known  responsibility. 
Hence,  the  commercial  conditions  prevailing  in  this  country  have 
enabled  these  firms  to  develop  extensive  equipments,  which  have 


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418       Alrich  on  Concrete  for  Gas  Holder  Tanks. 

wonderfully  facilitated  the  construction  of  steel  tanks.  When 
selecting  sites  for  large  holders  in  England,  they  appear  to  have 
generally  encountered  formations  of  clay  possessing  remarkable 
stability.  This  has  permitted  them  to  construct  economical 
tanks  by  lining  a  cylindrical  excavation  in  the  clay  with  brick 
walls,  which  are  thinner  than  our  geological  conditions  will 
generally  permit.  Unskilled  labor  is  relatively  very  cheap  in 
England,  and  in  some  cases,  the  cost  of  construction  has  been 
partly  defrayed  by  the  commercial  value  of  the  excavated  clay 
In  the  case  of  the  10,000,000-cu.  ft.  holder  erected  at  Manchester 
in  1909  and  1910,  the  brick  for  the  tank  walls  were  manufactured 
upon  the  site  from  the  excavated  clay.  It  is  a  fact,  however, 
that  the  time  required  for  the  construction  of  this  particular 
holder  would  be  regarded  as  economically  impossible  in  the 
United  States.  The  result  of  all  of  these  conditions  has  been 
that  the  English  holder  builders  have  not  developed  the  special 
equipment  required  for  the  construction  of  very  large  steel 
tanks,  nor  does  it  appear  that  the  British  steel  plants  produce 
plates  suitable  for  the  purpose. 

To  confine  the  discussion  now  to  American  conditions  the 
controlling  requirements  in  the  design  of  a  gas  holder  are: 

1.  Structural  Stability. 

2.  Economy. 

3.  Rapidity  of  Construction. 

4.  Durability. 

Certain  physical  phenomena  having  to  do  with  the  distribution 
of  gas,  require  the  holders  to  be  located  upon  the  lowest  avail- 
able ground.  In  this  coimtry  such  sites  rarely  consist  of  a  very 
stable  geological  formation,  and  are  frequently  reclaimed  land. 
Hence,  if  under  the  usual  conditions  there  be  undertaken  the 
construction  of  an  underground  masonry  tank,  there  will  probably 
be  encoimtered  such  diflSculties  as  to  greatly  enhance  the  cost 
of  the  work  and  prolong  the  period  of  construction.  If  it  should 
be  suggested  that  a  concrete  tank  might  be  built  above  the  ground, 
a  moment's  reflection  upon  its  relation  to  the  guide  frame  is  suffi- 
cient to  dispose  of  the  proposition. 

During  the  last  eight  years  the  writer  has  participated  in  the 
design  and  construction  of  the  three  largest  concrete  holder  tanks 
in  the  world.     Two  of  these  tanks  are  300  ft.  in  diameter  by  48 


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Alrich  on  Concrete  for  Gas  Holder  Tanks.        419 

ft.  3  in.  deep,  while  the  third  is  189  ft.  in  diameter  and  41  ft.  6  in. 
deep,  all  inside  dimensions.  In  referring  to  these  particular 
tanks,  and  also  throughout  the  discussion,  he  wishes  to  be  under- 
stood as  speaking  for  himself  alone.  The  work  on  these  three 
tanks  proceeded  in  such  simultaneous  relation  as  permitted  any 
improvement  in  methods  developed  on  one,  to  be  employed  to 
advantage  on  another. 

At  the  time  the  tanks  were  being  designed,  Mr.  William  H. 
Bradley,  the  Chief  Engineer  of  the  Consolidated  Gas  Company 
of  New  York,  made  a  thorough  inquiry  as  to  the  design  of  any 
other  concrete  tanks  that  had  been  constructed  anywhere  in 
the  world.  There  was  foimd  little  precedence  to  consider.  As 
regards  the  two  300-ft.  tanks,  the  undertaking  was  one  of  unusual 
n^agnitude,  for  the  holders  were  the  largest  that  have  ever  been 
built.  The  possibilities  of  nickel  steel  were  not  at  that  time 
fully  understood,  hence  the  construction  of  steel  tanks  would 
have  been  unthinkable,  as  there  would  have  been  required  plates 
4  in.  thick,  connected  by  rivets  3  in.  in  diameter.  It  was  evident 
that  masonry  construction  of  some  kind  must  be  employed.  A 
number  of  different  designs  were  worked  out,  analyzed  and  com- 
pared, resulting  in  the  conclusion  that  the  most  advantageous 
construction  would  be  a  plain  annular  wall  of  reinforced  concrete, 
and  all  three  tanks  were  thus  built.  The  work  upon  all  three 
tanks  was  accomplished  with  entire  success.  While  there  were 
special  conditions,  the  controlling  factors  in  these  instances, 
and  determining  the  selection  of  concrete  construction,  the 
writer  concludes  that  steel  is  far  preferable,  as  a  general  proposi- 
tion. The  smallest  of  these  three  tanks  required  a  full  year  for 
its  construction.  An  entire  holder  of  the  same  size  having  a 
steel  tank,  can  be  constructed  in  seven  months,  without  special 
effort.  It  has  also  been  demonstrated  to  the  satisfaction  of  the 
writer,  that  in  no  case  where  a  steel  tank  is  at  all  possible,  will 
the  cost  reach  70  per  cent  of  the  outlay  required  for  a  correspond- 
ing concrete  construction. 

The  question  as  to  whether  steel  or  concrete  tanks  are  the 
more  durable,  must  be  settled  in  another  generation;  but  the 
writer  believes  that  the  steel  tanks  are  the  more  expedient.  He 
has  knowledge  of  several  brick  tanks  having  been  badly  damaged 
by  blasting  in  their  vicinity.     From  his  knowledge  of  other  con- 


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420       Alrich  on  Concrete  for  Gas  Holder  Tanks. 

Crete  structures  having  been  badly  cracked  in  a  similar  way, 
he  must  conclude  that  concrete  tanks  are  not  immune  from  the 
hazard.  The  durability  of  concrete  tanks  is  also  open  to  question, 
in  view  of  the  peculiar  behavior  of  concrete  observed  by  the 
writer,  in  the  instance  of  two  of  the  most  prominent  engineering 
undertakings  in  the  United  States,  in  which  cases,  several  years 
after  the  concrete  had  set,  masses  of  it  became  soft  and  pulpy, 
requiring  replacement.  A  holder  tank  is  not  such  a  structure 
as  one  upon  which  such  repairs  can  be  easily  made,  but  it  is  one 
of  such  importance  as  to  forbid  speculative  constructions. 

The  writer  has  examined  and  reported  upon  a  large  number 
of  steel  tanks,  some  of  which  had  been  in  service  for  over  twenty 
years.  While  these  older  tanks  are  doubtless  constructed  of  a 
steel  far  inferior  to  that  which  is  now  produced,  all  of  these  tanks, 
with  one  exception,  could  survive  the  youngest  man  now  engaged 
in  the  gas  business.  It  has  sometimes  been  urged  against  the 
durability  of  steel  tanks,  that  all  favorable  conclusions  had  been 
formed  from  exterior  examinations.  The  writer  has  had  the 
opportunity  of  examining  internally,  some  of  the  oldest  steel 
tanks  in  existence,  through  which  he  concludes  that,  excepting 
at  the  water  line,  there  is  no  perceptible  deterioration.  In  one 
case,  the  holder  had  been  employed  for  twelve  years,  in  connec- 
tion with  a  process  of  gas  manufacture  now  obsolete.  As  a  part 
of  this  process,  a  non-luminous  gas  containing  some  sulphur 
was  stored  in  this  holder,  which  resulted  in  the  sulphur  being 
absorbed  by  the  water  in  the  tank.  The  writer  found  the  interior 
of  this  tank  to  be  but  very  slightly  pitted. 

The  writer  would  state  it  as  his  conviction,  that  while  not 
possessing  one  single  element  of  advantage  over  steel  tanks, 
that  concrete  tanks  are  subject  to  the  following  comparative 
disadvantages: 

1.  Increased  cost,  generally  75  per  cent, 

2.  Longer  period  required  for  construction,  generally  100 
per  cent  for  the  entire  holder. 

3.  Liability  to  impairment  from  unforeseen  or  unavoidable 
causes,  such  as  internal  stresses,  bad  water,  oil  or  alkaline  soil 
and  blasting. 

4.  Difficulty  of  making  repairs  and  obtaining  the  original 
strength  in  case  of  rupture. 


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AuacH  ON  Concrete  for  Gas  Holder  Tanks.       421 

5.  Possibility  of  corrosion  of  reinforcement,  the  vital  ele- 
ment of  the  tank's  strength. 

6.  Inaccessibility  of  metal  to  inspection. 

7.  Greater  load  on  fomidations. 

8.  Requires  the  most  rigid  inspection  and  supervision  to 
control  the  quality  of  the  work  during  construction. 

9.  Liability  to  serious  dfficulties  from  storms  during  con- 
struction, due  to  the  depth  of  excavation,  the  requirement  of 
maintaining  adjacent  streets,  requiring  sheet  piling  50  ft.  deep 
and  massive  shoring  timbers.  Also  liability  of  damage  to  the 
concrete  work  itself  from  the  same  cause. 

In  submitting  a  discussion  of  this  question  to  the  American 
Gas  Institute  in  1910,  the  writer  urged  the  following  as  the  twelve 
distinct  advantages  of  steel  tanks  when  compared  with  those  of 
masonry: 

1.  Less  cost. 

2.  Shorter  period  required  for  construction. 

3.  The  ease  with  which  the  quality  of  the  work  may  be  con- 
trolled during  construction. 

4.  The  high  state  of  development  in  fabrication  and  erec- 
tion. 

5.  Susceptibility  to  exact  computation  and  greater  reliability 
under  stress. 

6.  Accessibility  for  inspection. 

7.  Tank  may  be  placed  at  any  elevation  with  relation  to 
the  ground  line  that  may  be  desired. 

8.  No  liability  to  damage  by  storm  durmg  construction. 

9.  No  internal  stresses  from  shrinkage  or  temperature  that 
are  serious. 

10.  Possibility  of  rectifying  an  imequal  settlement. 

11.  No  liability  to  cracking  from  undetermined  causes. 

12.  The  ease  of  making  repairs  and  obtaining  the  original 
strength. 

Every  one  of  the  enumerated  disadvantages  of  concrete 
tanks,  and  advantages  of  steel  tanks  might  be  separately  ex- 
tended and  elaborated,  but  the  writer  will  confine  himself  to 
items  2  and  4  under  steel  tanks. 

The  bottom  of  a  steel  tank,  excepting  an  outer  course,  con- 
sists of  rectangular  steel  plates,  generally  about  f  in.  thick,  con- 


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422       Alrich  on  Concrete  for  Gas  Holder  Tanks. 

nected  by  single  riveted  lap  joints.  The  outer  course  consists 
of  heavy  segmental  plates,  which  conform  the  bottom  to  the 
circle.  Riveted  around  the  outer  edge  of  this  outer  course,  is 
the  bottom  curb,  which,  in  the  case  of  a  large  tank,  will  be  an 
8  X  8  X  IJ  in.  angle.  The  bottom  course  of  curved  plates,  form- 
ing the  shell  of  the  tank,  is  riveted  to  the  upstanding  leg  of  this 
curb  angle.  The  next  course  of  plating  is  then  attached  to  the 
lowest  course  by  a  single  riveted  lap  joint  running  horizontally 
around  the  tank  circumference.  The  other  courses  are  connected 
in  a  similar  manner,  the  entire  number  in  the  height  of  the  tank 
usually  being  about  eight  or  nine.  It  is  necessary  for  the  vertical 
joints,  which  occur  about  30  ft.  apart  around  the  circumference, 
to  be  spliced  in  a  manner  capable  of  resisting  the  full  circum- 
ferential tension.  To  accomplish  this,  the  joints  are  covered 
by  double  butt  straps,  each  such  splice  being  quadruple  riveted 
with  double  shear  rivets,  and  triple  riveted  with  single  shear 
rivets.  The  total  number  of  rivets  in  the  cylindrical  shell  of  the 
tank  alone,  may  be  as  many  as  25,000. 

After  the  bottom  of  the  tank  has  been  completed,  a  vertical 
steel  post  is  erected  at  its  geometric  center.  A  circular  rail  is 
also  laid  concentrically  upon  the  tank  bottom.  Mounted  upon 
trunnions,  upon  the  top  of  the  central  steel  post,  are  two  radial 
traveler  arms,  the  outer  ends  of  which  are  supported  by  legs 
having  wheels  running  upon  the  circular  rail.  These  radial 
travelers  are  equipped  with  such  suitable  attachments,  as  will 
permit  one  of  them  to  be  used  for  assembling  the  curved  plates 
while  the  other  supports  the  hydraulic-pneumatic  riveting 
machine.  Thus,  as  one  traveler  proceeds  around  the  circumfer- 
ence lifting  the  plates  into  position,  it  is  followed  by  the  other 
with  the  riveter.  Quite  obviously,  the  first  traveler  is  able  to 
keep  well  ahead  of  the  riveting,  which  permits  that  traveler  to 
participate  in  the  simultaneous  erection  of  the  five-holder  shells. 
When  the  tank  and  the  holder  sections  have  been  completed, 
the  tall  center  post  around  which  the  travelers  revolve,  is  replaced 
by  a  much  shorter  one,  resting  upon  the  center  of  the  crown, 
while  the  outer  leg  of  one  of  the  travelers  has  its  lower  section 
removed,  and  thus  shortened,  it  travels  upon  a  circular  rail  which 
has  been  attached  to  the  completed  crown.  The  other  radial 
traveler  is  entirely  removed.     After  water  has  been  placed  in  the 


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AuacH  ON  Concrete  for  Gas  Holder  Tanks.        423 

tank,  the  holder  is  gradually  inflated  with  air,  and  as  it  rises  the 
remaining  radial  traveler  moves  aromid  the  circumference,  erect- 
ing the  guide  frame  successively  in  tiers.  It  requires  but  little 
reflection  to  perceive  that  if  the  holder  is  to  be  provided  with  a 
concrete  tank,  any  such  co-ordination  is  impossible.  As  to  the 
time  required,  it  may  be  stated  that  in  the  instance  of  the  largest 
steel  tanks  ever  built,  which  were  251  ft.  3  in.  diameter,  the  lower 
courses  of  which  consisted  of  2]^-in.  plates  and  having  26  double 
butt  joints  in  each  course,  the  tanks  were  erected  and  riveted 
complete  at  the  rate  of  32  hours  per  course.  One  of  these  holders 
was  entirely  completed  in  7j  months.  If  there  be  a  method  of 
concrete  tank  construction  which  would  have  permitted  the 
completion  of  that  same  holder  in  two  years,  it  has  not  yet  been 
found. 

In  closing,  the  writer  will  condense  into  a  few  words,  his 
opinion  on  the  matter  as  stated  in  another  discussion.  "He  may 
be  charged  with  entertaining  a  strong  prejudice  against  masonry 
tanks.  He  will  admit  that  he  is  opposed  to  any  type  of  tank, 
25  to  40  per  cent  of  the  cost  of  which  may  go  into  digging  a  hole 
in  the  ground  instead  of  putting  quality  into  the  structure.'' 
To  this  he  would  add  his  conviction  that  a  site  which  forbids  a 
steel  tank  is  not  the  place  to  put  a  holder. 


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PROTECTION    OF    STEEL    IN    CATSKILL    AQUEDUCT 
PIPE  SIPHONS. 

By  Alfred  D.  Flinn.* 

Cement  manufacturers  and  many  cement  users  are  already 
so  familiar  with  the  Catskill  aqueduct  which  New  York  City  is 
building  to  convey  an  additional  supply  of  water  from  the  Catskill 
mountains  that  a  general  description  is  not  here  necessary.  This 
aqueduct  is  to  have  a  nominal  capacity  of  500,000;000  gallons 
daily.  In  the  92  miles  of  its  length,  it  crosses  14  minor  valleys 
where  metal  pipe  siphons  were  determined  upon  in  preference  to 
reinforced  concrete  pipes  or  deep  pressure  timnels  in  rock;  three 
of  these  siphons  are  west  of  the  Hudson  river,  and  eleven  east; 
in  seven  of  them  the  diameter  of  the  steel  shell  is  9  ft.  6  in.;  in 
four  this  diameter  is  9  ft.  9  in.,  and  in  the  remaining  three,  11  ft. 
3  in.  These  various  diameters  were  determined  by  an  economic 
distribution  of  the  available  fall  or  head.  The  length  of  the 
siphons  varies  from  608  to  6671  ft.;  one  of  the  U-ft.  siphons 
is  5584  ft.  long;  the  total  length  of  all  siphons  is  33,031  ft.  The 
thicknesses  of  plates  are  i^-,  i-,  xk-i  H"  a^^d  i"^^-  Th^  mairimum 
heads  on  the  siphons  range  from  50  to  340  ft.  With  one  excep- 
tion, each  siphon  rises  to  the  hydraulic  gradient  at  each  end  and 
is  there  connected  by  means  of  a  concrete  chamber  to  the  adjacent 
portions  of  the  cut-and-cbver  or  tunnel  aqueduct.  They  are  all 
of  open  hearth  steel.  Ultimately  there  will  be  3  pipes  in  each 
siphon,  in  order  that  the  siphons  may  have  the  full  capacity  of 
the  aqueduct  and  also  provide  for  one  pipe  being  temporarily 
out  of  service  for  cleaning,  repairs  or  renewal.  Only  the  middle 
pipe  of  each  siphon  is  being  laid  at  this  time.  The  7  more  northerly 
siphons  are  included  in  Contract  62  and  the  7  southerly  siphons 
in  Contract  68. 

For  years,  both  in  connection  with  the  work  of  the  Board 
of  Water  Supply  and  in  other  engagements,  several  of  the  Board's 
engineers  have  been  observing  the  results  obtained  by  coating 
steel  pipes  with  the  asphalt,  tar  and  other  dips  commonly  em- 

*  Department  Engineer,  Board  of  Water  Supply  of  the  City  of  New  York. 

(424) 


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Flinn  on  Protection  op  Steel  Pipe  with  Cement.    425 

ployed.  Study  had  also  been  made  of  some  special  forms  of 
protection  of  steel  pipes.  Excepting  Portland  cement  grout 
or  mortar  used  in  one  or  two  cases,  in  a  small  way,  none  of  the 
coatings  of  which  knowledge  could  be  had  gave  evidence  of  real 
permanence,  nor  have  they  been  fully  satisfactory  in  other  respects; 
therefore  it  was  decided  to  jacket  the  steel  pipes  of  the  aqueduct 
outside  with  rich  concrete,  and  to  line  them  with  Portland  cement 
mortar.  The  outside  concrete  was  to  have  a  minimum  thickness 
of  6  in.,  and  the  mortar  lining  a  thickness  of  not  less  than  2  in.; 
after  some  experimentation,  these  dimensions  were  definitely 
adopted,  as  shown  on  Fig.  1,  which  is  a  reproduction  of  the  draw- 
ing of  the  standard  types  of  pipe  construction. 

Means  for  applying  the  concrete  and  mortar  to  the  pipes 
so  as  to  attain  intimate,  complete  and  permanent  adhesion,  in 
spite  of  the  unavoidable  distortions  due  to  handling,  tempera- 
ture changes,  and  the  water  stresses,  were  studied,  along  with 
the  most  economical  and  feasible  methods  for  the  various  steps 
in  construction.  Preparation  of  the  steel  was  also  carefully 
studied.  Numerous  experiments  on  a  small  scale,  and  finally 
on  substantially  full-size,  were  conducted.  For  the  latter,  a  steel 
pipe  9  fib.  in  diameter  and  12  ft.  long,  of  |-in.  riveted  plates,  was 
lined  by  plastering  and  by  pouring  grout  or  very  thin  mortar 
into  the  space  between  a  cylindrical  form  and  the  inner  surface 
of  the  pipe.  In  the  plastering  experiments  several  kinds  of  metal 
reinforcement  were  tried;  also,  terra-cotta  and  cement  blocks 
or  tiles  were  bedded  on  mortar  and  plastered.  Briefly,  it  may 
be  stated  that  no  combination  of  plasterer's  skill,  with  the  various 
materials  suggested,  gave  linings  that  were  adequate  and  this 
method  was  expensive.  The  methods  using  sohd*tiles  or  blocks 
were  more  successful  than  those  using  any  form  of  metal  lath. 
But  when  removed,  all  the  plaster  coatings  showed  a  tendency 
to  separate  at  the  surfaces  between  the  successive  layers.  Grout- 
ing proved  by  far  the  most  satisfactory  and  least  expensive, 
and  was  adopted  as  the  basis  of  the  contracts. 

In  fabricating  the  pipes,  the  plates  were  bevel-planed  on 
their  edges,  then  punched  for  the  rivets  and  then  each  plate  was 
bent  to  proper  radius  by  bending  rolls.  This  bending  cracked 
the  mill  scale  and  removed  a  considerable  portion  of  it.  Pickling 
was  resorted  to  for  the  removal  of  the  remaining  mill  scale,  the 


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426    Flinn  on  Protection  of  Steel  Pipe  with  Cement. 


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Flinn  on  Protection  op  Steel  Pipe  with  Cement.    427 

rust  and  the  dirt.  Two  vertical  wooden  tanks  of  suitable  diam- 
eter were  placed  side  by  side,  one  containing  hot  dilute  sulphuric 
acid  kept  at  a  strength  of  about  5  per  cent  of  oil  of  vitriol,  which 
was  approximately  93  per  cent  pure  sulphuric  acid;  after  15 
minutes  in  this  solution  at  a  temperature  of  about  125  deg.  F.,  each 
plate  was  of  a  uniform  clear  steel  gray  color  all  over  and  when 
removed  was  at  once  dipped  into  clean  hot  water  in  the  adjacent 
tiank.  Riveting  followed  pickling  quickly,  the  pipes  being  made 
in  15-ft.  sections  of  2  rings  of  7^-ft.  net  length  each.  Each  ring 
Was  one  plate,  except  in  the  11-ft.  3-in.  pipes,  and  in  those  made 
of  plates  thicker  than  ^  in.,  for  which  two  plates  were  used.  It 
has  been  observed  that  where  steel  is  exposed  to  corrosion  with 
the  mill  scale  on  the  surface,  the  corrosion  tends  to  concentration 
at  certain  points  and  is  accompanied  with  pitting;  hence  the 
care  exercised  to  remove  the  mill  scale  thoroughly. 

Observation  and  such  information  as  was  available  indicated 
that  cement  mortar  adhered  most  strongly  to  steel  and  afforded 
the  best  protection  when  it  could  be  applied  directly  to  the  clean 
surface  of  the  metal.  Having  obtained  a  satisfactorily  clean 
surface  in  the  shop,  there  remained  the  problem  of  preserving  this 
surface  in  as  good  condition  as  practicable  until  the  pipes  could 
be  laid,  covered  with  the  concrete,  and  lined  with  the  mortar. 
Various  temporary  coatings  were  suggested,  but  it  was  finally 
decided  to  use  whitewash,  and  so  each  pipe  was  given  a  coat  of 
heavy  lime  whitewash  before  it  left  the  shop.  To  each  barrel 
of  whitewash,  about  50  gal.,  there  were  added  about  20  lb.  of  glue; 
the  glue  was  dissolved  in  water  before  mixing  in  the  whitewash. 
After  this  mixture  had  been  used  for  a  time,  about  1  lb.  of  Port- 
land cement  was  added  for  each  gallon  of  whitewash.  This 
whitewash,  applied  with  brushes,  did  not  adhere  very  well,  and 
through  lack  of  care  in  handling,  the  pipes  suffered  more  or  less 
almost  as  soon  as  it  was  applied.  They  suffered  more  from  expo- 
sure to  the  weather,  however,  than  from  abrasion;  but  even 
where  the  whitewash  was  not  disturbed  light  rusting  occurred. 
Only  around  the  rivets  and  at  joints  where  the  whitewash  had 
formed  a  very  thick  coating  was  there  no  sign  of  rusting.  Hence, 
as  delivered  at  the  trench,  the  pipes  had  more  or  less  complete 
coats  of  light  yellow  rust  very  uniformly  distributed  on  the  bared 
portions  of  the  steel,  without  indications  of  any  tendency  to 


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428    Flinn  on  Protection  op  Steel  Pipe  with  Cement. 

pitting.  This  light  rust  has  been  regarded  as  not  seriously 
objectionable. 

Probably  the  greatest  obstacle  to  securing  the  desired  pro- 
tection of  the  steel  between  the  time  it  leaves  the  shop  and  the 
time  it  is  covered  with  the  mortar  or  concrete  is  the  tendency  of 
the  steel  mill  and  fabricating  shop  to  push  their  operations  mu^h 
more  rapidly  than  the  pipe  can  be  laid,  tested,  and  covered^  and 
the  uncertainties  of  the  field  work,  which  make  it  desirable  to 
have  pipe  on  hand  ahead  of  the  progress  of  laying.  These  cir- 
cumstances resulted  in  some  cases  in  the  gradual  formation  of 
heavier  rust;  this  has  been  removed,  as  required  by  the  specifica- 
tions, as  is  also  the  whitewash  which  still  adheres  to  the  pipes, 
just  before  the  applications  of  the  jacket  or  lining. 

Ease  of  removal  and  probable  lack  of  objectionable  effects 
upon  the  mortar,  if  small  quantities  should  not  be  removed, 
were  among  the  reasons  for  adopting  whitewash.  Unquestion- 
ably, Portland  cement  grout  would  have  stuck  more  tenaciously, 
but  it  would  have  been  correspondingly  difficult  to  remove,  and 
it  was  thought  probable  that  the  mortar  of  the  lining  and  jacket 
would  not  adhere  well  to  the  old  cement  surface;  these  were 
considered  sufficient  arguments  for  forbidding  its  use.  For 
removing  the  rust  and  dirt  from  the  pipes,  wire  brushes  are  com- 
monly used,  and  in  some  of  the  worst  places  steel  scrapers  also. 
Inside  some  of  the  siphons  the  surfaces  have  been  rubbed  with 
empty  cement  bags  after  the  wire  brushing.  This  final  cleaning 
is  done  in  short  stretches  just  in  advance  of  the  placing  of  the 
concrete  or  mortar. 

To  support  the  pipe  in  the  trench  so  as  to  permit  the  placing 
of  the  concrete  jacket  beneath  it,  and  also  aid  in  bringing  the 
pipe  to  line  and  grade  as  it  was  being  laid,  concrete  blocks  called 
cradles  were  built  in  the  bottom  of  the  trench.  Figs.  2,  3  and  4 
show  the  several  styles.  At  first  attempts  were  made  to  have 
these  cradles  fit  the  bottom  of  the  pipe  closely,  but  this  gave 
trouble  and  the  shape  was  modified.  Some  cradles  were  made 
about  24  in.  square  and  extended  about  6  in.  below  the  ordinary 
sub-grade  of  the  trench,  with  their  tops  at  the  proper  grade  for 
the  bottom  of  the  pipe,  and,  on  the  whole,  this  shape  was  satis- 
factory. Some  of  the  longer  cradles  were  cracked,  due  probably 
to  unequal  bearing  or  shocks  in  placing  the  pipe.     Most  of  these 


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Flinn  on  Protection  op  Steel  Pipe  with  Cement.    429 


cracks  were  due  primarily  to  the  uneven  bearing  of  the  pipe  on 
the  cradles. 

The  pipe  having  been  laid,  riveted  and  calked  was  filled 
with  water  to  hydraulic  gradient,  inspected,  and  leaks  further 
calked.  Bulkheads  were  placed  in  the  open  ends  of  the  pipe  and 
a  small  riser  pipe  carried  up  to  the  proper  elevation  to  represent 


IS' 

4. 


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FIG.    2. — CONCRETE   CRADLES   FOR   PIPE   SIPHONS. 


the  working  head  when  the  aqueduct  would  be  in  service.  To 
maintain  this  pressure  on  the  pipe  constantly,  a  small  reservoir 
or  tank  was  attached  to  the  top  of  the  riser  pipe  and  kept  just 
spilling  over.  While  the  pipe  was  still  full  of  water  under  this 
normal  working  pressure,  the  concrete  jacket  was  placed  about 
it  by  methods  similar  to  those  used  in  building  concrete  conduit, 
excepting,  of  course,  that  no  inside  form  was  needed,  Figs.  5  and 


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430    Flinn  on  Protection  of  Steel  Pipe  with  Cement. 

6.  The  water  pressure  was  continued  until  this  concrete  had 
attained  considerable  strength,  the  period  depending  upon  the 
weather,  kind  of  cement,  and  other  conditions.  It  was  found 
undesirable  to  maintain  the  water  pressure  by  direct  pumping 
into  the  pipe  while  the  concrete  was  being  placed  and  was  harden- 
ing, since  fluctuations  of  head  caused  a  few  cracks.  Maintaining 
this  pressure  by  the  small  overflow  tank  and  riser  pipe  mentioned 
above  was  more  satisfactory.     When  the  last  concrete  was  suffi- 


(//?  roc/r  on/yj  /or /79/€fyo//ff 


FIG.  3. — TYPICAL  ARRANGEMENT  OF  CONCRETE  CRADLES  AND  JOINT  HOLES  FOR 

FIELD   RIVETING. 

ciently   hardened,   the  water  was  slowly   withdrawn  from  the 
pipe. 

Three  variations  in  the  procedure  of  placing* the  concrete 
jacket  were  tried:  (l)  Monolithic,  as  specified;  (2)  first  the  invert, 
then  the  remainder,  and  (3)  first  invert  and  side  walls  to  the  hori- 
zontal diameter,  and  then  the  arch.  The  best  contact  between 
the  jacket  and  the  pipe  seemed  to  have  been  obtained  when  the 
concrete  was  placed  monolithically.  It  was  found  unwise  to 
permit  the  concrete  to  be  dumped  from  the  buckets  with  a  greater 


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Flinn  on  Protection  of  Steel  Pipe  with  Cement.    431 

drop  than  2  ft.,  because  the  vibration  tended  to  crack  the  concrete 
recently  placed. 

On  one  siphon  the  average  rate  of  placing  concrete  jacket 
was  about  130  ft.  a  week;   on  another,  170  ft.;   and  on  a  third, 


PIG.   4. — LAYING   STEEL  PIPE   ON   CONCRETE   CRADLES. 

190  ft.,  the  maxima  on  these  three  siphons  being,  respectively, 
223  ft.  per  week,  297  ft.  and  260  ft.  On  one  siphon  the  progress 
of  30  ft.  of  full  section  per  8-hour  shift,  using  about  50  yd.  of 
concrete  mixed  by  machine  was  attained.     Many  factors  influ- 


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432    Flinn  on  Protection  of  Steel  Pipe  with  Cement. 

enced  progress,  such  as  the  method  of  mixing,  method  of  trans- 
portation whether  by  cableway,  wheelbarrows  or  cars,  and  the 
style  of  outside  forms,  whether  steel  or  wood,  and  the  conve- 
niences for  moving  and  setting  the  forms.  Earth  covering  was 
placed  in  many  cases  immediately  after  the  completion  of  the 
concrete  jacket,  but,  in  a  few  instances,  considerable  time  elapsed 
.  before  the  concrete  was  covered.  So  far  as  observed,  there  have 
been  few  cracks  in  the  concrete  jackets  built  to  the  end  of  last 
season.  • 


FIG.    5. — METHOD    OF    PLACING    CONCRETE   JACKET   AROUND   STEEL   PIPES. 

Two  quite  different  methods  were  at  first  tried  by  the  two 
contractors  for  lining  pipes.  Under  Contract  62,  the  contractor 
began  at  once  by  grouting  with  forms;  under  Contract  68,  an 
attempt  was  made  to  use  the  cement  gun,  and  the  Hunter's  Brook 
siphon,  1493  ft.  long,  9  ft.  9  in.  diameter  of  pipe  shell,  was  lined 
in  this  way.  The  cement  gun*  was  fully  described  in  Engineer- 
ing Recordf  July  1,  1911,  and  other  descriptions  have  been  pub- 
lished, so  that  it  need  not  be  described  again  in  this  paper.    Several 

*  See  Proceeding*,  Vol.  VII.  p.  504.— Eo. 


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Flinn  on  Protection  op  Steel  Pipe  with  Cement.      433 

machines  are  shown  m  Fig.  7.  Charges  of  dry  sand  and  cement 
mixed  in  prescribed  proportions  were  placed  in  the  charging 
chamber  of  the  machine  and  then  dropped  into  the  pressure 
chamber.  From  the  latter  the  mixture  was  rapidly  discharged 
under  an  air  pressure  of  50  to  60  lb.  per  sq.  in.  through  a  rubber 
hose,  while  through  a  parallel  hose  joining  the  former  in  a  special 
nozzle,  water  under  pressure  was  discharged  so  that  the  sprays 
of  water  and  of  sand  and  cement  were  commingled.  A  pressure 
of  about  30  lb.  was  maintained  at  the  nozzle  and  so  the  mixture 


FIG.   6. — ONE   OF  THE   CONCRETE   MIXERS. 

was  thrown  with  considerable  force  against  the  surface  being 
coated.  This  aided  in  securing  an  excellent  union  between  the 
mortar  and  the  steel  and  more  especially  between  the  successive 
portions  or  layers  of  the  lining.  The  operator  held  the  nozzle 
2  or  3  ft.  away  from  the  surface  being  coated,  moving  it  back 
and  forth  continuously,  meanwhile  controlling  the  discharge  from 
the  nozzle  by  lever  valves. 

The  force  with  which  the  mixture  of  sand,  cement  and  water 
is  thrown  against  the  surface  being  covered  causes  a  measurable 


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434       Flinn  on  Protection  of  Steel  Pipe  with  Cement. 

proportion  of  the  sand  grains  to  rebound  from  the  surface  and 
fall  into  the  bottom  of  the  pipe,  particularly  when  begiiming  the 
first  layer  on  the  bare  steel.  By  analysis  this  dry  material  was 
found  to  contain  about  1  part  of  cement  to  3f  parts  sand;  it  was 
collected  and  used  for  making  the  invert  or  bottom  part  of  the 
pipe  lining,  which  was  deposited  as  a  mortar  and  screeded  to 
shape  in  advance  of  the  gun  work.  Because  of  this  separation 
of  sand,  an  excess  of  it  is  put  into  the  dry  mixture  in  order  to 
prevent  the  lining  being  richer  than  intended.     Another  result 


FIG.    7. — FOUR   CEMENT   GUNS   ON   HUNTER's   BROOK   SIPHON. 

is  that  the  atmosphere  inside  the  pipe  is  commonly  very  dusty 
and  in  order  to  make  reasonable  working  conditions  for  the  men 
artificial  ventilation  was  resorted  to.  Furthermore,  the  mortar 
thus  applied  contained  less  water  than  the  grout,  and  more  atten- 
tion must  be  given  to  keeping  the  lining  moist  in  order  to  minimize 
shrinkage  cracks.  Fine  cracks  have  formed  rather  numerously 
and  are  probably  due,  in  considerable  measure,  to  the  failure 
to  keep  the  lining  wet  enough  while  it  was  setting  and  hardening. 
In  spite  of  the  difficulties,  a  lining  which  up  to  date  seems  satis- 
factory was  secured.     When  this  siphon  was  completed,  the  use 


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Flinn  on  Protection  of  Steel  Pipe  with  Cement.      435 

of  the  cement  gun  was  discontinued,  the  contractor  giving  as  a 
reason  excessive  cost.  Lining  by  the  grouting  method  was  then 
adopted  under  Contract  68. 

It  has  been  common  practice  to  place  the  lining  in  the  invert 
of  the  pipe  by  screeding,  the  width  thus  placed  varjring  from 
about  2  to  6  ft.  measured  along  the  arc.  Practical  difficulties 
prevented  the  use  of  a  simple  complete  cylindrical  form;  among 
th^e  difficulties  were  going  around  curves,  either  vertical  or 
horizontal,  collapsing  one  set  of  forms  sufficiently  to  pass  it  for- 
ward through  another  set  which  must  remain  in  place  while  the 
grout  was  hardening,  and  cleaning,  lubricating  and  inspecting  the 
outside  of  the  form  inside  the  pipe.  Consequently,  forms  in 
panels  about  2  ft.  wide  and  15  ft.  long  (7^  ft.  at  curves)  were 
adopted.  These  are  supported  on  wooden  ribs  or  centers  adjusted 
to  give  the  proper  thickness  of  lining  and  firmly  braced,  Fig.  8. 
The  lining  has  been  commonly  poured  in  15-ft.  sections  in  one 
operation. 

The  grout  is  poured  from  outside  the  pipe  through  a  2i-in. 
wrought-iron  pipe  secured  into  a  rivet-passing  hole.  In  the 
Southern  Department  this  pouring  pipe  is  at  the  downhill  end 
of  the  section  and  is  long  enough  to  give  a  head  of  about  4  ft. 
on  top  of  the  uphill  end.  A  vent  pipe  is  fastened  in  the  uphill 
rivet-passing  hole  of  the  section,  the  bulkhead  forming  the  end  of 
the  lining  being  placed  just  below  it.  For  poiu'ing  grout  the  con- 
tractor for  the  northern  siphons  has  always  used  two  mortar 
boxes  set  on  a  temporary  staging  over  the  upper  end  of  the  sec- 
tion to  be  grouted.  The  mortar  is  mixed  to  the  proper  consistency 
in  alternate  boxes  and  is  allowed  to  flow  into  the  pipe  through  a 
hole  controlled  by  a  sUding  wooden  gate.  All  mixing  is  done  by 
hand,  and  materials  are  carefully  graded.  It  generally  takes 
about  two  hours  to  fill  a  section,  after  which  a  man  is  kept  on  for 
an  hour  or  two  in  order  to  feed  in  sufficient  grout  to  get  the  desired 
consistency.  There  is  a  noticeable  tendency  to  get  a  porous  or 
thin  condition  at  the  upper  end  of  the  section,  near  the  grouting 
hole.  To  avoid  this,  the  riser  is  removed  two  or  three  times  dur- 
ing the  pouring  and  the  thin  material  which  collects  at  the  top  is 
allowed  to  escape.  The  riser  is  then  put  back  and  grout  added 
until  desired  results  are  obtained.  In  some  cases  it  takes  nearly 
two  hours  after  the  main  operation  to  get  grout  of  proper  con- 


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436      Flinn  on  Protection  of  Steel  Pipe  with  Cebient. 

sistency  at  the  foot  of  the  riser.  At  the  finish  of  the  pouring  a 
small  pipe  is  inserted  through  the  large  pipe,  to  permit  the  escape 
of  the  last  air  while  grout  is  poured  through  the  larger  pipe  and 
churned  into  the  small  remaining  space,  to  insure  complete  fiUing. 
For  the  first  batches,  or  nearly  up  to  the  horizontal  diameter  of 


FIG.   8. — WOODEN   FORMS  IN   PANELS   FOR   PLACING    CONCRETE  LINING  BY   THE 
GROUTING   METHOD. 

the  pipe,  the  grout  is  mixed  1  part  cement  to  1  part  sand,  and  the 
remainder  about  1  to  2. 

Some  fine  cracking  has  occurred  in  the  lining  placed  by  the 
grouting  method  as  well  as  in  that  deposited  by  the  cement  gun. 
None  of  this  cracking  is  believed  to  be  serious.  As  an  aid  to 
preventing  cracks  and  a  safeguard  against  the  remote  possibility 
of  small  pieces  of  the  lining  becoming  loose  and  falling  out,  both 
contracts  provide  for  using  wire  fabric  in  the  mortar,  as  a  rein- 


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FiiiNN  ON  Protection  of  Steel  Pipe  with  Ceiosnt.      437 

foroement,  but  up  to  the  end  of  last  year  none  had  been  used. 
Permanent  absolute  adhesion  of  the  concrete  or  mortar  to  the 
steel  IS  not  being  attained  at  all  parts;  this  has  been  proven  by 
careful  sounding  with  a  hammer,  but  on  cutting  into  hollow  sound- 
ing spaces,  the  space  between  the  mortar  or  concrete  and  the 
metal  has  been  found  almost  infinitesimal  in  width.  Before 
preparing  the  contracts,  such  an  occurrence  was  anticipated  and 
some  tests  were  made  at  the  Board's  laboratory  to  help  in  deter- 
mining how  serious  a  matter  this  would  be.  A  brief  statement 
of  these  experiments  follows: 

One  experiment  was  made  as  follows:  Four  circular  slabs 
15J  in.  diameter  and  3  in.  thick  were  made  of  concrete  in  pro- 
portions 1  cement:  2.7  Jerome  Park  screenings:  6.3  Jerome  Park 
stone  (gneiss)  by  weight,  the  consistency  of  the  mix  being  rather 
dry.  Carefully  imbedded  in  the  center  of  the  slabs  were  four 
i-in.  round,  softnsteel  rods  spaced  3  in.*  apart,  so  that  there  was 
at  least  IJ  in.  of  concrete  in  all  directions  from  each  rod.  When 
the  concrete  had  set,  two  of  these  slabs  were  immersed  in  water 
in  two  tanks  1  ft.  6  in.  in  diameter  and  2  ft.  deep.  The  other  two 
slabs  had  two  galvanized-iron  cylinders  15^  in.  in  diameter 
cemented  to  them,  and  a  head  of  20  in.  of  water  maintained  on 
them.  The  water  in  the  tanks  and  cylinders  was  kept  at  a  constant 
depth  and  head  by  the  addition  of  water  whenever  it  was  neces- 
sary. The  slabs  subjected  to  percolation  leaked  rapidly  at  first, 
but  became  gradually  tighter,  and  during  the  last  few  months 
of  the  tests  there  was  very  little  leakage.  The  tests  were  con- 
ducted in  open  air,  and  were  subject  to  the  variations  in  outdoor 
temperature.  The  tests  commenced  July  13,  1907.  On  March 
23,  1909,  one  year  and  eight  months  later,  the  slabs  were  broken 
and  rods  examined  for  corrosion.  It  was  found  that  the  pro- 
tection of  the  rods  by  the  concrete  was  perfect  in  all  cases,  there 
being  no  sign  of  corrosion  on  either  the  black  finish  of  the  metal 
left  by  the  rolls  or  on  the  bright  ends  of  the  rods  exposed  in  cutting 
to  length  with  the  hacksaw.  The  concrete  when  broken  was 
found  to  be  thoroughly  saturated,  showing  that  the  water  had 
full  access  to  the  rods. 

Another  experiment  was  conducted  as  follows:  Six  steel 
plates  8  in.  by  16  in.,  of  12  gauge,  cleaned  by  pickling  and  then  by 
rubbing  with  emery  cloth,  were  placed  horizontally  in  a  galvanized 


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438      Flinn  on  Protection  op  Steel  Pipe  with  Cement. 

iron  tank  18  in.  in  diameter  and  24  in.  deep,  separated  from  the 
bottom  by  two  IJ-in.  bars  of  alberene  stone,  and  from  each  other 
by  i-in.  wood  dowels.  The  first  pair  of  plates  was  put  in  with- 
out any  protective  covering.  The  second  pair  had  their  upper 
surfaces  protected  by  a  slab  of  cement  mortar  2i  in.  thick,  not  in 
contact  with  the  steel,  but  separated  from  it  by  two  metal  strips 
about  .04  in.  thick.  The  third  pair  of  plates  was  protected  by 
cement  mortar  slabs  2  in.  thick,  cast  directly  on  the  steel,  and 
apparently  adhering  to  it  firmly.  The  tank  was  then  filled  with 
proton  water  to  a  depth  of  4  in.  above  the  top  of  the  uppermost 
mortar  slab  and  kept  filled  the  entire  duration  of  the  test,  the 
water  being  renewed  twice  monthly. 

After  two  years'  immersion,  the  plates  were  taken  out  and 
cleaned  oflf  by  washing  with  a  sponge.  The  first  pair  of  plates 
showed  heavy  corrosion.  In  numerous  places  the  entire  layer  of 
oxide  had  separated  from  the  steel  and  formed  blisters,  leaving 
the  bright  steel  surface  underneath.  The  second  pair  of  plates 
showed  a  very  slight  corrosion.  Most  of  this  washed  off,  thus 
indicating  a  considerable  protective  infiuence  of  the  mortar  slabs 
even  when  separated  from  the  metal  by  a  space  of  .04  in.,  open 
at  the  edges  all  around.  When  the  mortar  slabs  were  removed 
from  the  third  pair  of  plates,  it  was  found  that  a  part  of  the  sur- 
face of  the  steel  had  a  distinctly  different  appearance  from  the 
other  part.  One  part  was  clean  and  wet;  the  other  part  was 
covered  by  strongly  adhering  particles  of  mortar  and  was  dry, 
thus  indicating  that  there  had  been  actual  adhesion  of  the  mortar 
only  over  the  latter  part  of  the  surface  and  that  the  former  had 
been  separated  by  a  space  large  enough  for  the  water  to  enter. 
There  had,  however,  been  no  rusting  except  at  some  places  near 
the  edges  of  the  wet  part  of  the  surface,  where  apparently  the 
space  had  been  big  enough  to  allow  circulation  of  the  water. 
The  water  in  the  rest  of  the  space  had  evidently  been  so  highly 
charged  with  lime  that  no  corrosion  could  take  place. 


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Flinn  on  Protection  of  Steel  Pipe  with  Cement.      439 

Extracts  from  Contract  62. 
general  sections. 
Order  of  Work, 
Sec.  19.    The  steel  pipe  shall  be  laid,  tested,  and  made  tight  against 
hydrostatic  pressure;  then  surrounded  by  concrete  while  still  under  the  normal 
hydrostatic  pressiu-e,  after  which  the  mortar  lining  shall  be  placed.     Except 
at  overhead  stream  crossings,  no  stretch  of  pipe  shaU  be  left  not  well  protected 
from  frost  between  stretches  of  pipe  around  which  concrete  has  been  placed. 
As  soon  as  practicable  after  the  concrete  covering  and  mortar  lining  have  been 
placed,  the  pipe  shall  be  covered  with  earth;  and  all  pipe  covered  with  con- 
crete, whether  or  not  mortar  lining  had  been  placed  in  it,  shall  be  protected 
in  freezing  weather  by  at  least  one  foot  of  earth. 

MORTAR  UNINO  FOR  STEEL  PIPES. 

(Item  26.) 
Work  Included. 
Sec.  26.1.    Under  Item  26  the  contractor  shall  build  a  mortar  lining 
inside  the  steel  pipe  and  cast-iron  bell  castings  as  specified,  directed  or 
approved. 

Description  and  Proportions, 
Sec.  26.2.  The  lining  shall  consist  of  Portland  cement  and  sand,  mixeJ 
in  ordered  proportions,  probably  one  part  of  cement  to  two  parts  of  sand 
The  quality  of  the  sand  shall  be  as  specified  under  Items  28  to  30.  Reinforce- 
ment, if  used,  will  be  paid  for  under  Item  27.  The  lining  shall  be  of  sub- 
stantially uniform  thickness  throughout  the  entire  circumference  except  for 
the  unavoidable  variations  due  to  lap  of  the  plates,  butt  straps,  and  rivet 
heads.  The  thickness  over  the  inner  course  of  plates  is  to  be  2  in.,  that  is, 
the  internal  diameter  of  the  lining  shall  be  4  in.  less  than  the  nominal  diameter 
of  the  steel  shell. 

Forms. 
Sec.  26.3.  Forms  shall  be  of  steel,  or  of  wood  covered  with  galvanized 
sheet  steel,  and  shall  be  especially  constructed  so  as  to  have  sufficient  strength 
and  yet  be  adjustable  so  as  to  give  a  uniform  space  between  them  and  the  shell 
of  the  pipe.  Great  care  shall  be  exercised  to  secure  forms  which  will  leave  the 
surface  of  the  lining  perfectly  smooth.  Forms  which  give  unsatisfactory 
results  after  use  shall  be  satisfactorily  repaired  or  replaced.  The  length  of 
the  sections  of  forms  will  not  be  restricted  provided  satisfactory  means  are 
adopted  for  controlling  the  uniform  thickness  of  the  lining  and  the  correct 
spacing  of  the  reinforcement,  but  sufficient  sections  shall  be  provided  adapted 
for  lining  the  pipe  on  curves,  where  lining  shaU  be  placed  in  sections  about  7  ft. 
long.  Each  time  the  forms  are  used  they  shaU  be  thoroughly  cleaned  and  then 
coated  with  some  approved  inadhesive  substance  which  wiU  prevent  the  mortar 
from  sticking  to  the  forms  without  injuring  the  mortar.    The  lining  of  manhole 


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440      Flinn  on  Protection  op  Steel  Pipe  with  Cement. 

castings,  and  of  the  blow-off  elbows  to  the  sockets,  shall  be  monolithic  with 
the  lining  of  the  steel  shell,  and  forms  shall  be  so  constructed  as  to  permit  this 
method. 

Method  of  Placing. 
Sec.  26.4.  The  lining  shall  in  general  be  placed  by  pouring  a  grout 
around  an  internal  form,  through  holes  cut  in  the  top  of  the  pipe  for  that  pur- 
pose in  the  manner  and  at  locations  specified  in  Section  19.11.  Sections  shall 
be  so  terminated  as  to  bring  a  hole  at  the  upper  end  which  shall  be  arranged  as 
an  air  vent.  The  mortar  shall  be  mixed  to  a  thick  creamy  consistency  and 
allowed  to  flow  into  place  as  uniformly  as  possible.  When  the  section  is  filled 
to  the  top,  the  pouring  of  the  grout  shall  be  continued  until  grout  runs  from 
the  air  vent;  then  headers  of  steel  pipe  shall  be  screwed  into  the  inlet  and  out- 
let holes  and  filled  with  grout  so  as  to  put  a  head  of  at  least  4  ft.  on  the  highest 
part  of  the  section,  and  these  headers  shall  be  kept  filled  with  grout  until 
the  grout  has  set,  when  the  pipe  shall  be  removed  and  the  hole  made  water- 
tight by  a  screw  plug.  During  the  pouring  of  the  grout,  the  form  shall  be 
tapped  to  loosen  air  bubbles,  and  a  careful  watch  shall  be  maintained  to  pre- 
vent leaks.  The  work  shall  be  so  planned  that  the  grout  can  be  poured  con- 
tinuously from  start  to  finish  of  the  section.  Any  interruption  greater  than 
fifteen  minutes,  whether  due  to  leaks  or  any  other  cause,  may  be  sufficient 
reason  for  the  rejection  of  the  entire  section. 

Lining  with  Plaster. 
Sec.  26.5.  Should  there  be  any  portion  of  the  interior  of  the  pipe 
which  it  is  impracticable  to  line  by  grouting,  this  portion  shall  be  lined  by 
plastering  the  pipe  with  mortar,  mixed  as  specified  in  Section  26.2.  Only 
skilled  masons  or  plasterers  shall  be  allowed  to  do  this  plastering,  and  a  section 
once  started  shall  be  prosecuted  imtil  finished,  with  only  such  pauses  as  are 
necessary  for  a  sufficient  setting  of  a  layer  to  permit  the  next  layer  to  be  placed. 
Each  layer  shall  be  as  thick  as  is  feasible  to  apply,  so  that  as  few  layers  as 
possible  may  be  necessary.  The  surface  of  each  layer,  except  the  final  one, 
shall  be  brushed  to  thoroughly  remove  the  laitance  and  then  deeply  scratched 
or  otherwise  satisfactorily  treated  to  give  a  bond  with  the  succeeding  layer. 

Removal  of  Forma. 

Sec.  26.6.  The  forms  shall  be  removed  within  twelve  houTB  of  the  time 
set  by  the  engineer,  and  the  section,  if  accepted,  shall  receive  immediately 
such  repairs  as  required,  in  the  manner  directed.  It  is  possible  that  the  lower 
part  of  the  Lining  will,  in  many  cases,  show  a  sandy  surface,  and  if  so,  it  shall 
be  brushed  with  enough  neat  cement  wash  to  fiU  the  pores  and  no  more,  and 
troweled  to  a  smooth  finish.  Any  section  not  accepted  shall  be  immediately 
removed  by  the  contractor  at  his  own  expense  and  replaced  by  acceptable 
lining. 

Prevention  of  Freezing;  Bvlkheada. 

Sec.  26.7.  Suitable  bulkheads  shall  be  erected  in  the  pipe  to  prevent 
freezing  inside  the  pipe  cither  during  the  placing  of  the  Lining  or  after  its 


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Flinn  on  Protection  of  Steel  Pipe  with  Cement.      441 

completion.  They  shall  be  removed  before  the  completion  of  the  contract, 
if  ordered.  Lining  shall  not  be  placed  in  the  uncovered  pipes  over  streams 
during,  or  within  a  month  before,  freezing  weather,  unless  the  pipe  is  satis- 
factorily protected,  and,  after  lining  these  portions  of  the  pipe,  water  shall  not 
be  allowed  to  stand  and  freeze  there. 

Measurement  and  Payment. 

Sec.  26.8.  For  placing  the  lining  in  the  steel  pipe  and  cast-iron  bell 
castings,  the  contractor  shall  receive  the  price  per  linear  foot  of  pipe  stipulated, 
the  measurement  to  be  made  along  the  axis  of  the  pipe,  this  price  to  include 
all  labor  and  materials  necessary  to  complete  the  lining  in  a  thorough  and 
approved  manner  except  only  that  the  cement  required  will  be  paid  for  under 
Item  35  (Portland  cement). 


REINFORCEMENT  OF  MORTAR  LINING  FOR  STEEL  PIPES. 

(Item  27.) 

Description. 

Sec.  27.1.  Reinforcement  may  be  ordered  under  Item  27  for  any  part 
or  the  whole  of  the  mortar  lining.  The  reinforcing  material  shall  be  galvanized 
steel  mesh  of  a  style  and  weight  approved,  provided,  however,  that  no  rein- 
forcement shall  be  required  of  which  the  lowest  price  obtainable  by  the  con- 
tractor, f  .o.b.  New  York  City,  exceeds  f  cent  per  square  foot,  for  lots  of  10,000 
sq.  ft. 

Placing. 

Sec.  27.2.  The  reinforcement  shall  be  placed  approximately  in  the  center 
of  the  mortar  lining.  The  reinforcement  may  be  kept  away  from  the  pipe 
by  distorting  the  reinforcement  at  frequent  intervals,  so  as  to  make  points 
projecting  toward  the  pipe.  Unless  otherwise  permitted,  small  blocks  of 
mortar  shall  be  attached  to  the  reinforcement,  for  the  purpose  of  keeping  it 
away  from  the  form.  Metal  shall  be  lapped  at  least  6  in.  at  all  longitudinal 
joints. 

Measurement  and  Payment. 

Sec.  27.3.  The  quantity  to  be  paid  for  under  Item  27  shall  be  the 
number  of  square  feet  of  lining,  meastu^  as  of  a  mean  diameter  9  ft.  4  in., 
in  which  reinforcement  has  been  ordered  and  placed.  This  does  not  include 
any  allowance  for  lap.  The  price  stipulated  shall  include  the  cost  of  the 
reinforcing  metal,  royalty  if  any,  cutting,  shaping,  bending,  wires,  clips,  mor- 
tar, and  other  devices  used  for  holding  the  reinforcement  in  place,  or  for  splic- 
ing the  strips;  and  it  shall  further  include  any  additional  expense  of  forms, 
tools,  appliances,  and  labor  other  than  the  expense  that  would  be  required 
for  finishing  the  mortar  lining  under  Item  26  without  reinforcement.  . 


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442      Flinn  on  Protection  of  Steel  Pipe  with  Cement. 

The  gain  in  smoothness  of  interior  by  covering  the  rivet 
heads  and  the  plate  laps  has  been  computed  to  so  increase  the 
hydraulic  capacity  that  three  pipes  equal  four  without  lining. 
The  total  cost  for  the  siphons  with  three  lined  and  jacketed 
pipes  is  estimated  at  about  the  same  as  for  four  pipes  constructed 
and  coated  in  the  more  usual  way.  Obvious  incidental  advantages 
are  secured  by  the  more  permanent  construction. 

The  Board  of  Water  Supply  of  the  City  of  New  York  is 


Table    I. — Contract  Prices  for  Steel  Pipes,    Concrete  Jacket   and 

Mortar  Lining. 


Description. 


Contract  62. 

9  ft.  6  in.  steel  pipe,  ^/u-in.  plate,  lap  jointed 

0  ft.  6  in.  steel  pipe,  V't-in.  plate,  lap  jointed 

9  ft.  6  in.  steel  pipe,  Vi-in.  plat«,  longitudinal 
jointed 

9  ft.  6  in.  steel  pipe,  */ia-in.  plate,  longitudinal  i 
jointed 

9  ft.  6  in.  steel  pipe.  "Ae-in.  plate,  longitudinal 

jointed 

9  ft.  6  in.  steel  pipe.  */4-in.  plate,  longitudinal  seams  butt- 
jointed 

Mortar  lining  for  steel  pipes 

Reinforcement  of  mortar  lining  for  steel  pipes 

Concrete  masonry  around  steel  pipes 

Portland  cement 


butt- 
biitt- 
biitt- 


Contract 
Price. 


Contract  Sfi. 

9  ft.  9  in.  steel  pipe,  "'kt-ia.  plate,  lap  jointed 

II  ft.  3  in.  steel  pipe,  ^/it-in.  plate,  lap  jointed.. . . 
11  ft.  3  in.  steel  pipe,  Vrin.  plate,  lap  jointed. . . . 
11  ft.  3  in.  steel  pipe,  ^/a-in.  plate,  longitudinal 

butt-jointed | 

11  ft.  3  in.  steel  pipe,  */i6  in.    plate,  longitudinal  seams 

butt-jointed ' 

Mortar  lining  for  9  ft.  9  in.  steel  pii)e ' 

Mortar  lining  for  11  ft.  3  in.  steel  pipe. ... 

Reinforcement  of  mortar  lining  for  steel  pipe. . . 

Concrete  masonry  around  steel  pipe 

Portland  cement 


$31.00  Un.  ft. 
36.00    "     " 

40.00    '•    " 

43.00    •'     •• 

47.00    "     " 

60.00    "     " 
2.50    '•    " 
.02  sq.    ft. 
6.00  cu.  yd. 
1.75  bbL 


t29.00  Un.  ft. 
33.00    ••    " 
88.00    •'     " 

46.00    "     •' 

50.00  "  " 
3.00  ••  '• 
3.50  "  " 
.02  sq.  ft. 
5.25  cu.  yd. 
1.60  bbl. 


Average  of 
AUBids. 


(5  bidder:) 

$35.50  Un.  ft. 

41.20    "    " 

44.80    "    " 

48.80    "    " 

66.80    "     " 

60.60    "     " 
4.90    "    " 

.03  0Q.  ft. 
6.86  cu.  yd. 
1.74  bbL 

i8  bidden.) 

$33.26     Un.  ft. 

37.37V«  "    " 

42.76      "    •• 

48.76      "    " 

63.62Vi  "  " 
3.56»/«  "  " 
4.04»/i  *'  " 
.02«/4  sq.  ft. 
6.78  ou.  yd. 
1.72t/s  bbL 


constructing  the  Catskill  Water. Works.  Engineering  operations 
are  being  directed  by  J.  Waldo  Smith,  chief  engineer;  Robert 
Ridgway  was  department  engineer,  Northern  Aqueduct  depart- 
ment, until  January  14,  1912;  Ralph  N.  Wheeler  was  appointed 
department  engineer  of  that  department,  February  1,  1912; 
Frank  E.  Winsor  is  department  engineer.  Southern  Aqueduct 
department.  In  immediate  charge  of  the  construction  of  the 
siphons  are  division  engineers  John  P.  Hogan,  Alexander  Thom- 
son, Jr,,  and  George  P.  Wood  (Northern);   George  G.  Honness, 


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Flinn  on  Protection  of  Steel  Pipe  with  Cement.      443 

Emest  W.  Clarke,  and  Charles  E.  Wells  (Southern).  The  draw- 
ings and  specifications  were  prepared  and  many  of  the  preliminary 
investigations  conducted  by  Senior  Designing  Engineer  Thomas 
H.  Wiggin,  and  Engineer  Inspector  Ernst  F.  Jonson  has  had 
charge  of  inspection  of  cement,  of  steel  at  the  rolling  mills  and 
of  pipe  at  the  shops,  all  under  the  immediate  supervision  of  the 
writer.  The  chief  engineer  and  his  personal  assistant,  Depart- 
ment Engineer  Thaddeus  Merriman,  made  many  examinations 
of  existing  steel  pipes  which  furnished  the  reasons  for  seeking  a 
better  protection  than  the  usual  coatings. 

All  drawings  reproduced  as  illustrations  are  for  the  9-ft. 
6-in.  pipes.  Corresponding  drawings  for  the  other  sizes  are 
similar;  likewise  standard  dimensions  for  rivet  and  joint  details. 


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A  FIREPROOF  SCHOOL  OF  CONCRETE. 
By  Theodore  H.  Skinner.* 

Early  in  the  winter  of  1910-11  the  writer  was  intrusted  by 
the  Trustees  of  Union  School  District  No.  12,  Town  of  Vernon 
and  City  of  Oneida,  N.  Y.,  with  the  task  of  building  a  new  four- 
classroom  school  house  which  should,  in  addition  to  complying 
with  all  the  regulations  of  the  New  York  State  Department  of 
Education,  be  as  nearly  fireproof  as  possible,  keep  within  an 
appropriation  of  $17,000,  be  so  arranged  as  to  appear  symmetrical 
and  complete,  while  in  reality  be  only  one-half  of  an  eight-room 
building  ultimately  desired.  The  school  house  shown  by  the 
accompanying  illustration  is  the  answer  to  the  many  problems 
involved  in  carrying  out  the  task. 

The  general  plans  were  gone  over  with  the  state  inspectors 
for  the  purpose  of  securing  informal  approval  of  same  before 
detailed  drawings  and  specifications  were  completed.  These 
plans  were  then  submitted  to  several  parties  with  requests  for 
estimates  and  sketches  showing  how  they  would  build  the  frame- 
work of  floors,  roof  and  enclosing  walls.  These  parties  repre- 
sented field-cast  reinforced  concrete,  light  steel  frame  with  metal 
lumber  and  metal  lath  stuccoed  and  factory-made  reinforced 
concrete. 

The  sketches  received  were  carefully  studied  and  general 
drawings  made  which  would  be  possible  to  follow  should  either 
system  be  selected.  Tenders  were  then  invited  from  a  number  of 
general  contractors.  The  specifications  provided  that  the  bidders 
might  use  either  one  of  the  three  systems  proposed  and  asked 
them  to  name  in  their  bid  what  would  be  the  difference  in  cost  of 
the  building  if  erected  by  them  under  the  various  systems.  The 
bids  ranged  from  $16,298.00  to  $24,500.00  for  the  bare  building 
"^dthout  plumbing  or  heating  and  nothing  to  spare  for  moving 
furniture,  etc.  The  local  contractor,  who  proved  to  be  lowest 
bidder,  then  opened  his  estimate  books  for  inspection  and  it  was 
found  that  by  combining  his  own  figures  for  portions  of  the  work 

♦  Architect,  Oneida,  N.  Y. 

(444) 


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Skinner  on  Fireproof  School  of  Concrete. 


445 


with  the  figures  named  by  the  party  bidding  on  factory  made 
reinforced  concrete  that  it  would  be  possible  to  carry  out  the  gen- 
eral plans  and  keep  within  the  appropriation.  Accordingly 
detailed  specifications  and  drawings  were  made  up  for  the  frame- 
work of  the  building  and  the  general  contract  let. 

The  building  (Figs.  1  and  2)  consists  of  a  rectangular  section 
25  X  92  ft.  running  north  and  south,  containing  four  classrooms 
each  24  x  32  ft.,  four  coatrooms  7  x  24  ft.,  stairway  11  ft.  wide, 
two  playrooms  in  the  basement  24  x  32  ft.,  separate  toilet  rooms 


FIG.    1. — KENWOOD   SCHOOL,    KENWOOD,    N.   Y. 

each  7  X  24  ft.  for  boys  and  girls  and  a  teachers'  room  11  x  13  ft. 
with  private  toilet  on  the  landing  over  the  first-  and  second-story 
stairway.  An  extension  across  the  front  13  x  40  ft.  contains  fur- 
nace room  in  the  basement,  and  is  entirely  corridor  on  the  two 
upper  floors.  There  are  two  minor  further  extensions  forming 
vestibules  at  front  and  rear. 

The  plans  (Fig.  3)  provide  for  two  additional  classrooms  at 
both  the  north  and  south  ends  of  the  present  rectangular  section 
to  be  reached  by  extensions  of  the  present  corridors  across  the 
west  or  blank  sides  of  the  present  classrooms.     Additional  stair- 


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446  Skinner  on  Fireproof  School  of  Concrete. 


{DiAACM^UX  ^UHj- 


-Lb li IJ-  -   r^Z 

CCCDDDDDD 
inGUDnDDDD 


Tim*  r^t^/a^TKm . 


FIG.  2. — GROUND  AND  FIR8T  FLOOR  PLANS,   KENWOOD  SCHOOL. 


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Skinner  on  Fireproof  School  of  Concrete.         447 

ways  will  be  provided  in  the  extended  corridors  and  also  coat- 
rooms  for  the  new  classrooms.  When  these  extensions  have  been 
made  the  west  or  street  face  of  the  building  which  now  presents 
large  blank  panels  will  be  symmetrical  on  the  center  line  of  the 
building  and  when  finished  will  have  large  windows  indicating 
the  lines  of  the  stairways. 

The  present  classrooms  have  southeastern  exposure  with 
unilateral  lighting  only.  The  coatrooms  are  accessible  only  from 
the  classrooms.  Each  classroom  is  provided  with  a  built-in 
cabinet  of  four  drawers  and  two  cupboards  for  the  teachers'  use 
and  has  blackboards  4  ft.  high  entirely  around  the  walls  except- 
ing for  the  window  spaces.  The  basement  rooms  are  10  ft.  in  the 
clear,  the  classrooms  12  ft.  The  plumbing  fixtures  are  all  of 
colonial  ware  and  of  the  latest  pattern,  two  drinking  fountains 
are  arranged  in  the  corridors,  one  in  each  story.  Special  anti- 
panic  exit  bolts  are  arranged  on  the  outside  doors,  which  open 
out. 

The  details  provided  for  a  steel  frame  for  the  classroom 
section,  of  12  columns  connected  by  horizontal  steel  girders  in  the 
plane  of  the  walls  at  several  points.  The  girders  carried  2  floors 
or  2  sets  of  separately  molded  and  cast  reinforced  concrete  joists, 
spaced  about  4  ft.  on  centers  which  rested  on  and  were  anchored 
to  them.  The  joists  carried  in  turn  a  series  of  ribbed  reinforced 
concrete  slabs  separately  molded  and  cast  in  the  factory  (Fig.  4). 
The  roof  was  constructed  in  same  maimer  as  the  floors,  the  only 
difference  being  that  the  joists  were  not  of  uniform  section 
throughout  being  severally  graded  or  warped  so  as  to  give  the 
roof  slabs  resting  on  them  the  proper  pitch  to  throw  the  water  to 
desired  points.  The  floors  and  roofs  of  corridors  and  entrance 
porches  were  built  also  of  separately  molded  members  supported 
by  bearing  walls  of  masonry.  The  type  of  imit  members  employed 
is  shown  in  Fig.  5. 

A  short  description  of  the  process  of  manufacturing  separately 
molded  reinforced  concrete  members  may  be  of  interest.  A 
frame  was  made  up  of  the  steel  rods  necessary  to  reinforce  the 
concrete,  carefully  designed  to  take  care  of  all  the  tensile  stresses 
which  might  be  developed  in  the  member  when  finished,  set  in 
place  and  loaded,  and  also  all  shear  which  the  concrete  would  not 
take  care  of.     Longitudinal  tension  rods  were  carefully  bent  to 


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448         Skinner  on  Fibepboof  School  of  Concrete. 


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Skinner  on  Fireproof  School  of  Concrete. 


449 


the  desired  form  and  united  into  rigid  frames  by  means  of  vertical 
loops  and  small  rods  womid  around  the  larger  ones  which  also 
take  care  of  the  shear.  Some  smaller  longitudinal  rods  were 
built  into  the  frames  at  their  tops  to  take  care  of  any  excessive 
compression  or  any  tension  which  might  be  caused  by  negative 
bending  moments  produced  in  handling  the  beams.  Special  loops 
were  attached  to  the  tension  rods  at  their  quarter-points  extend- 
ing up  above  the  top  rods  in  the  frames  and  above  the  finished 
concrete  at  the  top  by  which  the  beams  were  lifted,  the  strain  all 
coming  on  the  reinforcement. 


PIO.   4. — REINFORCED   CONCRETE   SLABS   IN   YARD   OP   CONTRACTOR. 

Sand  molds  were  prepared  on  large  casting  floors  of  the 
shape  desired  for  the  finished  beams  and  in  these  molds  the  unit 
reinforcing  frames  were  suspended  in  proper  place,  and  then 
liquid  concrete  was  poured  into  the  molds  and  thoroughly  worked 
in  and  around  the  reinforcement.  The  molds  were  filled  to  the 
top  and  struck  off  with  the  straight  edge.  A  mixture  of  1:2:4 
concrete  was  used,  the  largest  aggregate  passing  a  1-in.  screen. 

The  beams  were  allowed  to  remain  in  the  sand  7  days  after 
which  they  were  lifted  by  the  loops,  carried  by  a  traveling  crane 
into  an  open  yard  and  stored  until  ready  for  shipment. 


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The  manufacture  of  the  floor  panels  would  not  have  been 
possible  without  a  vibrating  machine.  A  frame  of  small  rods  to 
act  as  reinforcing  for  the  webs  was  first  made,  this  was  then 
covered  with  wire  reinforcement  well  wired  to  the  rods.  The 
frame  was  then  placed  in  molds  on  vibrating  machines;  the  con- 
crete poured  and  vibrated. 

The  beams  were  about  10  in.  wide,  18  to  24  in.  deep,  of  Tee 
section  with  the  top  edge  rebated  on  each  side  to  receive  the 
floor  slabs.  All  joists  were  approximately  25  ft.  long.  Floor 
slabs  were  about  4  ft.  square  webbed  or  thickened  around  the 
edges  and  once  across  the  middle  to  3  in.  thick,  the  centers  were 
thin  panels  only  IJ  in.  thick.     Joists  and  slabs  were  designed  to 


FIG.   5. — GENERAL  TYPE   OF   UNIT  CONCRETE  MEMBERS. 

carry  a  live  load  of  100  lb.  per  sq.  ft.  in  addition  to  their  own 
weight,  with  a  factor  of  safety  of  4. 

The  footings  for  the  12  columns  were  isolated,  7  ft.  square 
and  16  in.  thick.  The  basement  walls  between  the  columns  were 
made  of  12-in.  hollow  terra  cotta  tile  carried  by  independent 
footings.  The  tiles  were  laid  up  in  cement  mortar,  plastered  with 
cement  mortar  on  the  outside  and  coated  with  asphalt  up  to 
grade.  The  exterior  walls  between  columns  above  the  basement, 
being  curtain  walls  only,  were  laid  up  of  8-in.  hollow  terra  cotta 
tile  and  were  stuccoed  on  the  outside  and  plastered  on  the  inside. 
The  columns  and  girders  were  covered  with  metal  lath  and  con- 
creted in  solidly. 


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Skinner  on  Fireproof  School  of  Concrete.        451 

The  cornices  were  supported  by  a  cast  stone  bed  molding, 
ornamented  with  egg  dart  topped  out  with  a  12-in.  tile  covered 
with  stucco.  Some  small  brick  inserts  were  made  just  below  the 
cornice  to  relieve  the  absolute  monotony  of  the  color  of  the  stucco 
and  shallow  lines  were  drawn  in  the  stucco  facia  and  elsewhere 
while  it  was  still  soft  to  form  panels  and  accents.  With  these 
exceptions  the  exterior  is  a  plain  gray  floated-finish  cement 
stucco.  It  will  be  given  a  brush  coat  of  some  waterproof  cement 
stain  or  finish  before  another  winter  to  fill  up  minor  checks  and 
prevent  water  and  frost  damage. 

All  exterior  windows  were  combined  frame  and  sash  of  metal, 
glazed  with  clear  double-thick  glass  in  the  lower  panels  and  with 
rippled  glass  in  the  upper.  Each  sash  was  provided  with  2  ven- 
tilating sections. 

The  roof  is  a  flat  concrete  slab  pitching  only  enough  for 
drainage  from  the  level  verge  to  two  outlets  near  the  center  line. 
This  was  covered  with  5-ply  slag  and  composition  roofing  and  is 
not  visible  from  the  ground. 

The  interior  finish  was  the  simplest  possible.  The  masonry 
walls  were  plastered  with  two  coats  of  mortar  and  left  under  the 
float,  then  painted  4  ft.  high  with  oil  paint  two  coats,  and  above 
with  water  color  two  coats.  No  wood  trim  was  used  around 
either  doors  or  windows,  but  plank  jambs  of  wood  were  used  in 
the  doorways  to  which  the  doors  were  hung  by  pivot  hinges  at 
top  and  bottom.  No  wood  door  sills  were  used,  in  short  the  only 
wood  in  the  entire  building  being  the  door  jambs  and  doors,  the 
molding  at  the  top  and  bottom  of  blackboards,  cleats  for  coat 
hooks  in  the  wardrobes  and  panels  of  wood  flooring  in  the  center 
of  each  classroom. 

These  panels,  4  in  number,  were  laid  of  one  thickness  maple 
floor,  I  X  2J  in.  face  over  2  x  4  in.  hemlock  sleepers,  on  top  of  the 
concrete  construction  previously  described,  were  oiled  on  the 
under  side  before  being  laid  and  given  a  coat  of  oil  immediately 
after  laying  to  prevent  their  absorbing  water  from  the  composition 
borders,  subsequently  laid  against  them.  The  balance  of  the 
classroom  floors  were  finished  on  top  of  the  cement  slabs  with 
concrete  surfaced  with  colored  material  to  match  the  wood  center. 
These  borders  merged  into  a  sanitary  or  cove  base  4  in.  high 
everywhere.      Corridors,   stairways   and   wardrobes   all  have   a 


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Skinner  on  Fireproof  School  of  Concrete. 


granolithic  cement  coat  over  the  structural  concrete  slabs,  this 
finish  also  merging  into  a  sanitary  base  4  in.  high.  There  was  no 
projection  to  these  sanitary  bases  at  the  top,  the  same  being 
finished  flush  with  the  finish  plaster. 

The  four   classroom  ceilings  were  plastered  upon  expanded 
metal  lath  carried  by  angle-iron  furrings  which  in    turn  were 


FIO.    6. — CEILING   OF   PLAYROOM,    KENWOOD   SCHOOL. 

attached  to  numerous  iron  lugs  left  projecting  from  the  cast  con- 
crete floor  joists  for  this  purpose.  These  furred  ceilings  were 
used  for  a  double  purpose,  first  to  make  a  ceiling  free  from  all 
shadows,  and,  second,  to  provide  a  deadening  air  space  so  that  the 
noise  of  walking  on  the  top  of  the  concrete  construction  should 
not  be  heard  in  the  room  below.     The  basement,  corridor  and 


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Skinner  on  Fireproof  School  of  Concrete.         453 

stairway  ceilings  were  left  unfurred,  with  the  cast  joists  and  panel 
slab  construction  showing,  as  may  be  seen  in  Fig.  6,  all  painted 
with  water  color  paint  presenting  a  very  attractive  appearance. 

The  contract,  let  May  15,  1911,  provided  for  the  completion 
of  all  work  by  September  15,  but  delays  were  experienced  from 
the  start,  first  in  getting  the  necessary  steel  fabricated  and  later 
in  securing  competent  labor  for  erecting  the  steel  and  laying  the 
heavy  concrete  floor  and  roof  joists.  It  was  not  until  November 
26,  or  a  few  days  over  six  months  from  the  start,  that  the  work 
was  completed. 

The  joists  and  slabs  were  loaded  on  cars  at  the  factory  and 
shipped  by  local  freight  28  miles;  were  unloaded  by  means  of  a 
small  traveling  crane  on  to  farm  wagons  and  then  hauled  a  little 
better  than  a  mUe  to  the  job.  Here  they  were  unloaded  and 
swxmg  into  place  by  seemingly  inadequate  apparatus,  all  at  less 
expense  than  the  contractor  figured  he  could  erect  forms  and  cast 
the  same  number  of  members  in  situ.  The  joists  and  slabs  stood 
shipping  remarkably  Well  and  reached  the  job  in  good  condition 
in  spite  of  the  rough  handling  given  by  the  local  train,  on  which 
the  cars  are  shunted  back  and  forth  at  every  station  a  great  num- 
ber of  times.  Only  one  joist  and  four  slabs  required  replacing  as 
they  were  too  green  when  loaded,  30  days*  seasoning  should  be 
allowed  before  shipping. 

The  straightforwardness  of  the  various  operations  at  the 
building  appealed  both  to  the  general  contractor  and  to  the 
architect  as  it  offered  opportunity  to  inspect  each  member  before 
erection  and  the  job  was  not  littered  up  nor  complicated  with  the 
forest  of  supports  necessary  for  field  concrete  construction.  No 
unexpected  difficulties  were  encountered  and  no  members  failed 
to  fit  their  respective  locations  accurately,  and  everyone  con- 
nected with  the  work  would  be  satisfied  to  repeat  the  operation 
again,  with  the  exception  possibly  of  the  maker  of  the  cast  work, 
who  might  wish  to  add  slightly  to  the  original  allowance  for 
handling  the  cast  members  at  the  building. 

The  estimates  of  cost  for  the  various  types  of  construction 
not  used  were  perhaps  confidential  and  will  not  be  given  in  detail ; 
it  is  sufficient  to  say  that  they  were  higher  than  those  obtained 
for  the  construction  adopted. 


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454         Skinner  on  Fireproof  School  of  Concrete. 

The  contracts  for  the  building  as  erected  were  as  follows: 

Steel  frame $1,500.00 

Structural  concrete  floors,  roof  and  stairs 3,000 .  00 

Suspended  ceilings,  unplastered 225 .  00 

Granolithic  in  halls  and  coatrooms 196 .  00 

Colored  surfacing  and  sanitary  base  in  classroom 379.00 

Iron  stair  rails 200.00 

General  contract  for  balance  of  work  and  materials,  including  ex- 
cavation, grading,  carpentry,  painting,  etc 9,545.00 

$15,045.00 

Plumbing 767.00 

Heating 825.00 

Hardware 225.00 

Total $16,862.00 

In  addition  to  the  above  a  flowing  spring  was  encountered  in 
the  excavation  which  gave  standing  water  over  part  of  the  base- 
ment and  made  it  desirable  to  underdrain  same  and  waterproof 
basement  walls;  it  also  necessitated  a  change  in  the  plans  of  the 
cold-air  boxes  from  beneath  the  basement  floor  to  overhead. 
These  two  items  cost  respectively  $200.00  and  $227.97.  Some 
additional  fireproofing  of  steel  to  that  provided  under  the  con- 
tract was  thought  desirable  and  added  at  a  further  expense  of 
$400.00.  Cement  platforms  or  walks  outside  at  the  entrance 
cost  $38.00,  making  a  total  of  extras  on  the  work  over  and  above 
the  first  contracts  of  $863.97  and  bringing  the  total  cost  of  the 
building  as  delivered  by  the  contractor  to  the  Trustees,  $17,527.97. 

Not  coimting  the  area  of  vestibules,  this  building  has  an 
area  of  2820  sq.  ft.  on  the  ground,  is  40  ft.  from  bottom  of  base- 
ment floor  to  top  of  roof  and  contains  112,800  cu.  ft.  Its  cost 
per  cu.  ft.  is  15.5  cts.,  per  classroom  $4381.99  and  per  pupil  as 
$97.37. 


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THE  PRESENT  STATUS  OF  UNIT  CONCRETE 
CONSTRUCTION. 

By  James  L.  Darnell.* 

To  put  it  briefly  it  might  be  said  that  the  present  status  of 
Unit  Construction  is  one  of  progression.  Every  day  new  things 
are  developing  about  this  very  logical  and  rational  method  of 
constructing  and  erecting  concrete  structiures.  Within  the  past 
two  years  there  has  been  more  progress  in  both  the  design  and 
in  the  field  work,  that  is,  the  construction  and  erection  of  sep- 
arately molded  structures,  than  in  all  the  time  previous. 

In  heavier  structures,  such  as  bridges  and  viaducts,  the 
engineering  forces  of  the  Chicago,  Burlington  and  Quincy  Railway 
Company  under  the  direction  of  Mr.  C.  H.  Cartlidge,  Bridge 
Engineer,  and  of  Mr.  George  E.  Tebbetts,  now  bridge  engineer 
for  the  Kansas  City  Terminal  Railway  Company,  have  done 
much  valuable  work  and  they  have  pioneered  the  way  for  others 
less  advancced.  The  Chicago,  Milwaukee  and  St.  Paul  Railwaj'^ 
Company  under  Mr.  C.  F.  Loweth,  Chief  Engineer,  has  also 
done  some  work  in  this  line,  but  not  to  the  same  extent.  Mr. 
R.  E.  Gaut,  while  bridge  engineer  of  the  Illinois  Central  Railway 
Company,  also  used  this  system  in  the  design  of  highway  struc- 
tures in  connection  with  track  elevation  work  in  Chicago.  All 
of  this  work  was  successfully  done  and  showed  pronounced 
advantages  over  ordinary  methods. 

If  this  is  the  "Concrete  Age"  as  most  of  us  fondly  believe, 
it  will  certainly  come  to  pass  that  the  railroads  particularly  will 
have  to  adopt  unit  construction  methods  for  their  concrete  struc- 
tures because  it  lends  itself  with  peculiar  fitness  to  railway  work 
of  all  kinds  and  shows  such  marked  economies  in  both  time  and 
money,  that  ordinary  or  monolithic  construction  is  out  of  the 
question.  This  is  shown  in  the  present  track  work  of  the  Kansas 
City  Terminal  Railway  Company,  where  Mr.  Tebbetts  has 
adopted  this  form  of  construction  for  every  structure  along  the 

*  Manager.  Kansas  City  Unit  Construction  Company,  Kansas  City.  Mo. 

(455) 


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456  Darnell  on  Unit  Concrete  Construction. 

line  except  those  where  surrounding  conditions  are  such  that  the 
use  of  some  other  type  was  imperative,  as  the  McGee  Street 
Viaduct,  where  the  124-ft.  span  required  a  concrete  encased 
steel  girder. 

In  building  construction  the  progress  has  been  more  marked 
perhaps  than  in  bridges  and  viaducts.  The  first  recorded  example 
of  a  building  of  any  magnitude  built  of  separately  molded  units 
is  that  of  the  two  kiln  houses  for  the  Edison  Portland  Cement 
Company  at  New  Village,  N.  J.,  early  in  1907.*  These  two 
buildings  were  simple  one  story  sheds  of  the  plainest  possible 
type.  No  attempt  was  made  to  elaborate  or  to  refine  the  design, 
as  nothing  more  was  necessary  than  a  simple  assemblance  of 
columns,  roof  beams  and  roof  slabs.  In  these  two  sheds  however, 
the  soundness  of  the  principle  of  separately  molded  units  was 
demonstrated. 

At  about  this  same  time  the  idea  of  building  construction 
with  separately  molded  units  seems  to  have  been  taken  up  inde- 
pendently in  other  sections  of  the  country.  In  the  east  Mr. 
E.  L.  Ransome  was  developing  a  system  which  he  is  employing 
successfully  up  to  the  present  time.  Perhaps  the  most  notable 
example  of  the  Ransome  type  of  Unit  Construction  is  the  four 
story  building  60  ft.  x  200  ft.  built  for  the  United  Shoe  Machin- 
ery Company  at  Beverly,  Mass.  This  building  has  successfully 
met  all  its  requirements  and  is  in  every  respect  equal  to  and  in 
some  respects  superior  to  similar  buildings  of  ordinary  mono- 
lithic construction. 

Mr.  Charles  D.  Watson  of  Syracuse,  N.  Y.,  has  also  done 
considerable  work  along  this  line,  having  successfully  constructed 
several  separately  molded  buildings,  f 

In  St.  Louis,  at  about  this  same  time,  Mr.  Albert  J.  Meier 
in  conjunction  with  Mr.  John  E.  Conzelman,  at  that  time  engi- 
neer for  the  Corrugated  Bar  Company,  and  Mr.  C.  D.  Morely 
a  contractor,  were  working  to  perfect  a  Unit  system  independently 
and  without  knowledge  of  the  work  that  was  being  done  by  others. 
From  the  beginning  there  were  two  very  apparent  difficulties  to 
be  met  and  surmounted.  The  first  one  was  the  difficulty  in  devis- 
ing or  designing  connections  between  the  separately  molded  units 


♦  Seo  Proceedings,  Vol.  IV.  1908.  p.  48— Ed. 

t  See  ProceediTHjB,  Vol.  IV,  1908.  p.  97;   Vol.  VI.  1909,  p.  391. 


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Darnell  on  Unit  Concrete  Construction. 


457 


which  would  be  as  strong  as  the  units  themselves.  Second,  there 
were  well  taken  objections  on  the  part  of  many  people  to  sep- 
arately molded  buildings  of  concrete  on  account  of  the  pure  and 
monotonous  ugliness  of  such  buildings. 

The  first  difficulty,  that  of  the  connections,  has  been  most 
successfully  overcome  by  the  use  of  interlocking  and  overlapping 
reinforcement,  broad  bearings  and  improved  methods  of  grouting 
the  connections.  The  second  or  aesthetic  objection  is  being 
gradually  overcome  both  by  improved  and  advanced  design  and 
by  a  process  of  evolution,  in  which  the  engineer  in  designing  is 


FIG.  1. INTERIOR  OF  WAREHOUSE,  NATIONAL  LEAD  COMPANY,  KANSAS  CITY,  MO. 

slowly  but  surely  drawing  away  from  the  architectural  faults  of 
its  monolithic  predecessor.  The  progress  is  best  shown  in  the 
illustrations  which  follow. 

The  first  building  constructed  with  separately  molded 
units  by  the  Unit  Construction  Company  of  St.  Louis,  Mo., 
was  a  warehouse  for  the  National  Lead  Company,  erected  on 
West  Thirteenth  Street,  in  Kansas  City,  Fig.  1.  This  build- 
ing was  built  under  great  difficulties  in  a  very  restricted 
space.  It  was  attempted  to  mold  the  units  within  the  building 
lines,  which  proved  to  be  very  expensive  by  reason  of  the  neces- 


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Darnell  on  Unit  Concrete  Construction. 


sary  rehandling  of  the  unite  from  time  to  time.  Because  of  the 
unsightly  appearance  which  would  have  been  presented  by  the 
use  of  concrete  unite  in  the  front  of  the  building,  the  National 
Lead  Company  at  that  time  wanted  a  brick  face.  The  rear  of 
the  building,  however,  was  built  of  concrete  unite  and  ite  appear- 
ance in  a  measure  justifies  the  objections  of  the  owners  on  the 
score  of  unsightliness.  The  different  pointe  between  the  unite 
are  very  cleariy  indicated  and  while  the  wall  on  the  whole  does 
not  present  a  very  beautiful  appearance,  it  is  after  the  lapse  of 
some  four  years,  perfectly  serviceable,  thoroughly  substantial 
and  water-tight.     We  are  certainly  proud  of  this,  our  first  build- 


FIG.    2. CASTING    YARD    FOR   CONCRETE    UNITS. 

ing,  because  it  is  still  standing  up,  apparently  more  substantial 
than  when  built  and  because  it  has  been  so  thoroughly  satis- 
factory to  the  owners. 

This  first  building  was  so  successful  that  the  company  was 
enabled,  in  competition  with  various  other  contractors,  to  secure 
a  contract  for  a  very  much  more  extensive  construction  for  the 
National  Lead  Company  in  St.  Louis.  Fig.  2  is  a  general  view 
of  the  casting  yard  laid  out  for  this  construction.  Fortunately 
there  was  in  this  case  plenty  of  room  to  spread  out  in,  conse- 
quently it  was  not  necessary  to  cast  the  unite  on  the  ground 
within  the  building  lines.     An  extensive  plot  of  ground  was  avail- 


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Darnell  on  Unit  Concrete  Construction.  459 


FIG.   3. — SETTING    A   WALL   SLAB. 


FIG.   4. — ERECTION   OF   CORRODING   STACK  HOUSE,  ST.  LOUIS,  MO. 


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able  adjacent  to  the  site  of  the  building  and  thereon  was  erected 
the  construction  plant.  Concrete  materials  were  elevated  in  a 
belt  and  bucket  conveyer  from  cars  to  bins  in  the  top  of  the 
tower,  seen  in  the  left  center  of  the  picture.  Immediately  below 
these  bins  was  the  concrete  mixer,  which  discharged  by  gravity 
into  the  cars  on  the  oval  elevated  track.  Movable  spouts  con- 
ducted the  concrete  from  this  track  level  to  the  molds  for  the 
units  which  were  laid  horizontally  in  the  casting  yard.  A  travel- 
ing derrick  was  erected  to  run  between  the  elevated  tracks  and 
was  used  to  handle  the  completed  units  from  the  yard  onto  flat 
cars  for  conveyance  to  the  building  site. 


FIG.  5. — ROOF  SHOWING  CONCRETE  SKYLIGHTS  AND  LOUVRES. 

Fig.  3  is  a  view  of  the  building  after  construction  had  some- 
what further  progressed.  This  shows  many  of  the  columns  in 
place  and  the  workmen  setting  a  partition  slab.  It  may  be  seen 
that  the  foundations  were  run  in  monolithically  with  slots  left 
for  the  reception  of  the  columns.  A  key  was  cast  in  each  slot 
to  engage  a  corresponding  slot  cast  in  the  columns,  both  of  which 
may  be  plainly  seen  in  the  picture.  Fig.  4  shows  a  view  of  the 
structtire  when  about  two-thirds  complete.  This  view  illustrates 
another  advantage  of  unit  construction  in  that  as  soon  as  any 
part  of  the  building  is  in  place  it  is  ready  for  service.  This  was 
peculiarly  demonstrated  in  this  particular  building.  To  make 
room  for  this  structure  it  was  necessary  to  dismantle  and  tear 


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461 


down  the  old  wooden  stack  building  and  necessarily  the  machine 
capacity  was  seriously  impaired.  It  proved  to  be  of  great 
advantage  that  after  four  or  five  bays  were  finished,  they  were 
turned  over  for  service.  As  it  happened  the  compan}*-  was 
making  white  lead  in  more  than  three-fourths  of  the  building  by 
the  time  it  was  finally  completed.  Fig.  5  is  a  view  of  the  roof 
of  this  same  building,  showing  the  sky  lights  and  louvres,  and 
illustrates  the  roof  construction  which  was  of  the  regulation  felt, 
tar  and  gravel  type.  This  building  when  complete  was  750  ft. 
long,  105  ft.  wide  and  about  45  ft.  high. 

Fig.  6  is  a  group  of  three  buildings  built  for  the  National 
Lead  Company  at  their  St.  Louis  plant,  contracts  for  which  were 


FIG.   6. — lU  1LDINCJ8   OF    NATIONAL    LEAD    COMPANY,    ST.    LOUIS,    MO. 

secured  after  the  stack  house  had  progressed  pretty  well  along 
toward  completion.  This  group  consists  of  an  office  and  welfare 
building  on  the  right,  an  oil  house  in  the  center,  and  a  stable 
and  garage  on  the  left  of  the  picture.  In  this  group  is  seen 
something  of  the  architectural  progress  which  was  referred  to 
earlier  in  this  paper.  They  certainly  present  a  not  unpleasant 
appearance  and  we  think  they  appear  favorably  with  some  build- 
ings of  similar  type  in  any  material. 

Figs.  7  and  8  represent  the  most  pretentious  structure  which 
has  engaged  the  attention  of  the  Unit  Construction  Company 
up  to  the  present  time.  This  is  an  oxide  mill  also  for  the  National 
Lead  Company,  built  in  St.  Louis,  which  provided  for  floor  loads 
running  from  500  lb.  on  the  first  floor  to  250  lb.  on  the  top  floor. 


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462  Darnell  on  Unit  Concrete  Construction. 


"^ 

FIG.    7. — OXIDE    MILL   IN    COURSE   OF   ERECTION,    FIVE   STORIES. 


fc  ,-  _J^ 

FIG.   8. — OXIDE  MILL  BUILDING   COMPLETED. 


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Darnell  on  Unit  Concrete  Construction. 


463 


A  study  of  these  views  will  give  to  the  observer  an  excellent 
idea  of  the  construction  methods  employed  as  nearly  all  of  the 
details  may  be  observed. 

Fig.  9  shows  a  corroding  stack  building  erected  for  the 
National  Lead  Company  at  New  Kensington,  Pa.  They  are 
interesting  in  that  they  show  architectural  progress  as  well  as 
improvement,  both  in  design  and  workmanship. 

Last  year  the  first  contract  was  taken  for  a  50,000  bushel 


FIG.     9. — CORRODING   STACK   BUILDING,    NATIONAL   LEAD   COMPANY, 
NEW   KENSINGTON,    PA. 

grain  elevator,  Fig.  10,  for  the  Highland  Milling  Company  at 
Highland,  111.  In  this  case  each  slab  unit  had  a  column  cast  on 
the  end  of  it  and  the  whole  was  held  together  by  big  rods  running 
entirely  through  the  building  with  large  cast  washers  on  the 
outside.  This  elevator  had  nine  bins  in  it;  eight  were  storage 
bins  and  the  ninth  carried  the  elevating  machinery.  This  struc- 
ture has  been  in  service  for  more  than  a  year  and  the  owners  of 
the  Highland  Milling  Company  are  very  enthusiastic  advocates 
of  Unit  concrete  construction  because  during  a  season  in  which 


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464 


Darnell  on  Unit  Concrete  Construction. 


it  was  very  hard  owing  to  weather  conditions  to  successfully 
store  grain,  in  this  elevator  not  a  bushel  was  lost. 

A  building  under  construction  for  the  Ohio  Cultivator  Com- 
pany at  Bellevue,  Ohio  is  shown  in  Fig.  11.  This  building  is 
200  ft.  square,  three  stories  high  with  a  high  basement. 


FIG.    10. — GRAIN   ELEVATOR,    HIGHLAND   MILLING   COMPANY,    HIGHLAND,   ILL. 

As  to  the  use  of  Unit  construction  in  railway  work,  Fig.  12 
shows  a  reinforced  concrete  crossing  at  Sangoman  Street  in 
Chicago,  111.  The  work  of  the  Kansas  City  Terminal  Railway 
Company  where  concrete  units  are  being  used  for  all  the  via- 
ducts and  subways  required  in  the  Terminal  Company's  improve- 


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Darnell  on  Unit  Concrete  Construction. 


465 


ments,  which  are  now  going  on,  includes  some  forty  structures 
in  all.  Fig.  13  shows  a  unit  bridge;  Fig.  14  column  molds  as 
well  as  some  of  the  finished  columns;  Fig.  15  shows  an  outer 
deck  slab  which  carries  the  coping  and  panel  fascia. 

The  pictures  show  for  themselves  the  present  status  of  Unit 
Construction  both  as  applied  to  buildings  and  to  bridges  and 
kindred  structures. 

A  word  as  to  the  '*why"  of  unit  construction.       At  first 


FIG.   11. — BUILDING  FOR  OHIO  CULTIVATOR  COMPANY,  BELLEVUE,  OHIO. 

glance,  to  an  engineer,  the  system  looks  novel  and  interesting, 
but  of  narrow  application  and  of  little  practical  value  or  utility. 
Invariably,  however,  after  thorough  study  the  engineer  becomes 
more  and  more  convinced  of  the  practicability  of  the  system  and 
of  its  broad  and  diverse  possibilities.  In  fact  those  who  are  con- 
nected with  its  application  cannot  find  the  time  to  go  into  the 
many  virgin  fields  of  construction  effort,  but  up  to  the  present 
have  been  compelled  to  devote  all  their  time  and  energies  to 
the  development  of  the  single  field  of  mill  and  warehouse  con- 


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Darnell  on  Unit  Concrete  Construction. 


struction  with  short  excursions  into  the  grain  elevator  and  rail- 
way fields. 

For   unit   construction   are   claimed  all  the  advantages  of 


FIG.  12. — CONCRETE  BRIDGE  CROSSING,  SANGOMAN  STREET,  CHICAGO,  ILL. 


FIG.  13. — RAILROAD  BRIDGE  OF  UNIT  CONCRETE  COLUMNS,  BEAMS  AND  SLABS. 

permanency,  strength  and  ultimate  economy  to  which  structures 
of  reinforced  concrete  are  justly  entitled,  without  any  of  the 
disadvantages  and  uncertainties  which  in  the  structure  built  by 


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Darnell  on  Unit  Concrete  Construction. 


467 


ordinary  methods  are  so  often  attended  by  unfortunate  results — 
accidents  which  are  always  serious,  sometimes  fatal. 

By  this  method  the  designer  is  sure  that  no  expansion  joints 


FIG.  14. — UNIT  CONCRETE  COLUMNS  AND  MOLDS. 


FIO.  15. — UNIT  CONCRETE  DECK  SLAB  WITH  COPING. 

will  open  up  in  unexpected  places  because  of  improper  deposition 
of  concrete  or  other  carelessness  of  the  workmen.  Each  unit 
member  of  the  structure  is  built  on  the  ground  under  practically 


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468  Darnell  on  Unit  Concrete  Construction. 

factory  conditions.  Eflfectual  inspection  is  assured  in  all  respects. 
The  reinforcement  is  placed  where  the  engineer  designed  it  to 
be;  each  unit  is  a  true  monolith  without  seam  or  flaw;  each 
unit  is  properly  cured  and  is  prepared  in  the  building;  the  pos- 
sibility of  getting  an  imperfect  column,  beam,  girder  or  slab  into 
a  structure  is  entirely  eliminated.  In  short,  the  manufacturing 
conditions  of  the  units  make  for  a  maximum  of  efficiency  in  all 
departments  with  the  chance  for  uncertainties  reduced  to  prac- 
tically a  negligible  quantity.  In  erection  the  same  condition 
prevails  as  the  mechanical  handling  of  the  units  is  exactly  the 
same  as  in  the  handling  of  steel  and  with  properly  designed  units 
it  is  practically  impossible  to  go  wrong  on  the  connections. 

Unit  Construction  today  is  just  beginning  to  come  into  its 
own.  Its  application  is  wide  and  the  genius  of  the  American 
engineer  will  soon  lead  to  the  general  adoption  of  a  system  which 
combines  in  itself  the  maximum  of  efficiency,  economy  and 
permanency  and  minimizes  the  uncertainties  contingent  on  the 
vagaries  of  the  American  workingman — ^who  is  principally  a 
foreigner. 


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DISCUSSION. 


Mr.  Rudolph  P.  Miller. — Mr.  Chairman,  I  would  like  to  Mr.Muier. 
inquire  if  the  joints  must  not  be  filled  up  on  the  work  and  whether 
any  attempt  is  made  to  carry  the  reinforcement  from  one  member 
to  an  adjoining  member  so  as  to  effect  continuity? 

Mr.  James  L.  Darnell. — ^The  joints  and  connections  are  Mr.  Dameu. 
all  grouted  in.  The  reinforcement  overlaps  and  interlocks,  i.e. 
goes  through  the  connection  which  results  in  practically  a  mono- 
lith. In  fact,  extensive  laboratory  tests  show  that  the  connec* 
tions  are  stronger  than  the  units  themselves.  It  has  been  demon- 
strated in  buildings  actually  constructed  and  in  service  that  the 
connections  are  the  strongest  part  of  the  structiu'e. 

Mr.  John  E.  Conzelman. — ^The  question  just  asked  would  Mr.  conzciman. 
indicate  that  there  was  some  doubt  in  the  speaker's  mind  as 
to  the  stability  or  rigidity  of  the  buildings  and  I  want  to  say 
that  the  buildings  we  have  constructed  seem  to  be  just  as  rigid 
and  stable  as  similar  buildings  constructed  in  the  ordinary 
manner.  In  fact  after  the  joints  are  poured  a  imit  constructed 
building  has  the  advantages  of  continuous  action  and  rigidity 
characteristic  of  buildings  made  by  the  ordinary  or  monolithic 
method.  It  may  be  interesting  to  know  that  the  thin  walls  used 
on  these  buildings  have  proven  satisfactory.  We  have  con- 
structed seven  or  eight  buildings  with  three  and  four  inch  walls 
which  have  passed  through  two  winters  with  no  complaints  from 
the  owners. 

Mr.  E.  J.  Moore. — The  question  of  shrinkage  cracks  in  Mr.  Moore, 
floors  seems  to  be  important.  The  speaker  referred  to  the  absence 
of  cracks  in  the  floors.  Cracks  from  temperature  stresses  will 
no  doubt  occur  at  the  joints  where  the  different  sections  are  put 
together  and  that  would  seem  to  make  an  added  problem  of 
waterproofing  the  joints. 

Mr.   Conzelman. — Mr.   Darnell   stated   that   cracks  often  Mr.  conzeiman. 
occurred  in  concrete  structures  built  in  the  usual  way  and  that 
these  cracks  did  not  at  all  times  select  their  location  with  due 
regard  for  the  appearance  of  the  structure  or  the  feeling  of  the 
builder;   in  fact  these  cracks  often  appear  at  imfortunate  places. 

(469) 


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470        Discussion  on  Unit  Concrete  Construction. 

Mr.  ConzeinuiA.  It  is  unusual  to  866  a  long  concr6t6  retaining  wall  or  building  in 
which  there  are  not  some  cracks.  These  cracks  (neglecting  settle- 
ment or  other  structural  causes)  are  due  to  two  causes,  shrinkage 
of  the  concrete  as  it  dries  out  and  temperature  changes,  acting 
separately  or  in  combination. 

A  great  many  of  the  cracks  are  due  to  shrinkage  stresses 
but  in  unit  construction  these  stresses  are  practically  elminated. 
This  is  due  to  the  fact  that  each  vmit  has  hardened  before  it  is 
incorporated  into  the  building.  The  unit  itself  may  have  some 
slight  internal  stresses  due  to  shrinkage,  but  these  are  not  cumula- 
tive and  do  not  affect  the  complete  structure.  Each  unit  takes 
care  of  itself. 

Temperature  stresses  cannot  be  eliminated,  although  tem- 
perature changes  undoubtedly  have  less  effect  on  unit  construc- 
tion than  on  monolothic,  on  the  same  principle  that  a  brick  wall 
(which  is  constructed  of  small  units)  will  generally  show  fewer 
cracks  than  a  concrete  wall.  We  have  observed  this  action  care- 
fully and  have  had  very  little  difficulty,  if  any,  from  temperature 
effects  and  account  for  it  by  the  fact  that  during  the  construction 
of  the  building  and  before  the  connections  are  grouted,  the  imits 
attain  an  average  temperature. 

Mr.  Moore.  Mr.  Moore. — I  take  it  therefore  that  it  is  necessary  to 

waterproof  most  of  this  filling.  Joints  in  factory  floors  are  more 
especially  referred  to  as  these  are  washed  down  and  there  is 
objection  to  having  the  water  go  through  the  cracks. 

Mr.  conxeinum.  Mr.    Conzelman. — ^Thc    construction   shown   is   absolutely 

waterproof  so  far  as  we  know.  A  unit  weighing  4  or  5  tons 
when  set  on.  a  mortar  bed  will  compress  it  to  such  an  extent 
that  it  is  practically  watertight.  One  advantage  of  unit  con- 
struction is  that  we  know  just  where  the  joints  are  and  as  leak- 
age is  necessarily  confined  to  the  joints  proper  provision  can  be 
made. 

Mr.  Kinney.  Mr.   William   M.   Kinney. — It  would  secm  there  would 

certainly  be  some  little  unevenness,  which  is  one  of  the  greatest 
troubles  of  the  concrete  floor  and  one  of  the  things  we  are  trying 
to  eUminate  in  floors  that  have  to  be  trucked  over.  The  trouble 
occurs  where  the  joints  are  made  in  a  floor  and  the  question 
arises  whether  in  unit  construction  any  {protection  is  afforded 
over  the  joints. 


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Discussion  on  Unit  Concrete  Construction.        471 

Mr.  Darnell. — ^There  is  no  apparent  joint  at  the  edge  of  Mr.  Dameu. 
the  floor  slabs.  The  floor  slab  and  beam  are  cast  in  one  and 
the  edges  of  the  slabs  are  made  so  that  the  space  between  is  in 
the  form  of  a  wedge,  which  is  filled  up  level  with  mortar  so  that 
practically  there  is  no  joint  left  at  all  and  the  floor  is  perfectly 
smooth.  That  is  perhaps  one  of  the  advantages  of  this  form  of 
construction.  The  edge  of  the  floor  slab  is  built  to  exact  dimen- 
sions and  if  any  vmevenness  develops  it  is  very  easy  in  setting 
the  slab  on  the  girder  to  level  it  up  smoothly,  which  is  done. 
If  the  levelling  is  carefully  done  and  these  wedge  shaped  joints 
filled  up  with  grout,  it  makes  the  floor,  to  all  intents  and  pur- 
poses so  far  as  the  surface  is  concerned,  perfectly  smooth.  There 
has  been  no  trouble  with  uneven  joints  in  trucking  over  floors 
in  any  of  the  buildings.  The  National  Lead  Company's  buildings 
in  St.  Louis,  is  a  group  in  which  trucking  is  constantly  going  on 
and  there  has  never  been  a  complaint  at  any  time. 

Mr.  Allen  Brett. — ^The  tests  reported  by  the  Committee  Mr.  Brett, 
on  Reinforced  Concrete  and  Building  Laws,  in  the  case  of  the 
beam  and  slab  show  that  the  concrete  in  the  slab  acts  in  com- 
pression practically  all  the  way  across.  This  girder  used  in  unit 
construction  is  a  broad  inverted  T,  practically,  and  the  slabs  are 
inverted  boxes,  the  edges  of  which  rest  on  the  flange  of  the  T. 
Is  there  any  compression  acting  with  the  girder  in  the  slab? 

Mr.  Conzelman. — ^The  girders  are  made  with  ledges  or  Mr.  conzeinum. 
shelves  on  each  side  upon  which  rest  the  floor  slabs,  usually  made 
to  resemble  the  cover  of  a  large  box.  They  consist  essentially 
of  a  thin  plate  or  slab  carried  by  beams  on  each  side,  these  beams 
returning  arovmd  the  ends  of  the  slab;  the  arrangement  gives  the 
slabs  a  continuous  or  uniform  bearing  on  the  girder  ledge.  The 
thickness  of  the  slab  or  plate  may  vary  from  IJ  to  5  or  6  in. 
depending  on  the  load  to  be  carried  and  the  span  between  beams. 
When  the  slabs  are  placed  the  top  of  the  slab  is  higher  than  the 
top  of  the  girder,  an  amovmt  equal  to  the  thickness  of  the  slab, 
and  the  steel  projecting  from  the  slabs  on  each  side  of  the  girder 
interlock  in  the  space  so  formed;  the  stirrups  from  the  girder 
also  extend  into  this  space.  The  joints  between  the  girder  and 
slabs  are  then  grouted  and  the  space  filled  with  a  rich  concrete. 
After  the  grout  has  hardened  these  become  for  all  practical  pur- 
poses T  beam  sections. 


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472        DiscuBsioN  ON  Unit  Concrete  Construction. 

Mr.  cm&zeiiiuui.  This  T-beam  action  has  been  demonstrated  in  the  laboratory 

on  large  beams  by  measuring  the  deformation  in  the  concrete 
directly  over  the  girder  and  in  the  adjoining  floor  slabs  and  also 
the  deformation  of  the  reinfprcement,  by  means  of  an  extenso- 
meter  similar  to  that  which  has  been  described  by  the  Com- 
mittee on  Reinforced  Concrete. 

Mr.  H.  p.  Green.  Mr.  HERBERT  P.  Green. — What  provision  is  made  to  take 

up  the  shear  between  the  columns  other  than  the  brackets  on  the 
columns? 

Mr.  Conzeinum.  Mr.  Conzelman. — The  brackets  are  designed  to  take  the 

entire  load  from  the  girder;  the  brackets  are  designed  for  ver- 
tical shear  and  bending  moment.  The  size  of  the  top  of  the 
bracket  is  determined  by  the  bearing  area  required  to  properly 
distribute  the  load  from  the  girder  to  the  bracket. 


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REPORT  OF   COMMITTEE  ON   SPECIFICATIONS   AND 
METHODS  OF  TESTS  FOR  CONCRETE  MATERIALS. 

In  this  first  report  of  the  Committee  no  definite  recommenda- 
tions are  presented  for  specific  tests  or  methods  of  making  tests 
of  aggregate,  except  that  the  Committee  reconmiends  for  a  practi- 
cal test  of  sand  a  determination  of  the  strength  of  mortar  made 
with  it.  The  report,  therefore,  is  in  the  nature  of  a  tentative 
discussion  of  various  tests  and  of  methods  that  have  been  used 
in  diflFerent  laboratories.  This  progress  report  should  be  followed 
during  the  coming  year  by  further  investigations  leading  to  more 
definite  reconmiendations. 

The  Committee  request  that  information  on  methods  of  mak- 
ing tests  of  aggregates  and  results  obtained  by  such  methods  be 
forwarded  to  the  chairman  of  the  committee.  Laboratories  that 
are  in  a  position  to  assist  the  Committee  or  imdertake  research 
work  in  the  line  of  concrete  aggregates  are  also  asked  to  corre- 
spond with  the  Committee. 

Importance  of  Testing  the  Aggregates. 

The  selection  of  aggregates  for  concrete,  especially  the  selec- 
tion of  sand  or  fine  aggregate,  is  of  as  great  importance  as  the 
selection  of  the  cement.  So  evident  is  this  to  the  engineer  who  has 
had  experience  both  in  practical  construction  and  in  laboratory 
tests,  that  it  is  almost  inconceivable  that  so  much  important 
work  should  be  undertaken  and  carried  through  without  testing 
the  sand.  Frequently  every  carload  of  cement  is  carefully  sampled, 
but  no  test  whatever,  except  by  inspection,  is  made  of  the  equally 
important  ingredient,  sand.  When  tests  are  made,  they  frequently 
are  confined  to  mechanical  analysis  or  granulometric  composition. 
While  this  is  a  valuable  test  for  comparing  the  qualities  of  different 
fine  aggregates  that  other  tests  have  shown  to  contain  no  impuri- 
ties, it  does  not  show  up  some  of  the  worst  defects  that  occur 
occasionally.     It  therefore  cannot  be  relied  upon  alone. 

The  impossibility  of  determining  the  true  quality  of  a  siand 
or  other  fine  aggregates  by  mere  inspection  cannot  be  emphasized 
too  strongly. 

(473) 


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474  Report  on  Tests  for  Concrete  Materials. 

Sampling  Aooreoates. 

Samples  must  be  taken  in  such  a  way  as  to  obtain  a  fair 
average  of  the  material  to  be  tested. 

The  size  of  the  sample  depends  upon  the  character  of  the 
aggregate  and  the  nature  of  the  test.  One  should  err  on  the  side 
of  getting  too  large  a  sample  rather  than  one  that  is  too  small. 
For  tensile  or  compressive  tests  of  mortar  made  with  fine  aggre- 
gate a  sample  not  less  than  20  lbs.  in  weight  should  be  taken  in 
order  to  have  enough  material  left  over  for  other  laboratory  tests 
that  may  be  deemed  necessary.  If  practical  tests  of  proportions 
with  coarse  aggregates  are  to  be  made,  the  sample  of  fine  aggregate 
should  be  several  times  larger  than  this. 

The  coarse  aggregate  sample  should  be  larger  than  that  of 
the  fine  aggregate  in  order  to  get  fair  average  of  the  material, 
because  the  grains  are  larger  and  there  is  more  variation  in  them. 
Whatever  tests  are  made  must  be  on  a  larger  scale.  For  tests 
involving  both  mechanical  analysis  and  volumetric  tests  of  con- 
crete mixtures  for  proportioning  the  aggregates,  at  least  200  lbs. 
of  each  coarse  aggregate  are  needed. 

Samples  should  be  shipped  in  a  strong  box  or  a  bag.  It  is 
advisable  also  that  the  natural  moisture  be  retained  as  far  as  po"^- 
sible,  so  that  the  laboratory  will  receive  the  material  in  its  natural 
condition. 

For  sub-dividing  the  sample  to  obtain  the  required  amount 
for  each  test,  different  methods  are  employed  in  different  labora- 
tories.   One  of  the  common  methods  is  that  of  quartering. 

Quartering. — To  quarter  a  sample  of  aggregate,  it  is  spread 
out  on  a  thoroughly  clean  floor  or  table,  or  else  upon  a  large  sheet 
of  manilla  paper.  Care  is  used  in  spreading  to  see  that  particles 
of  different  size  are  distributed  through  the  mass.  The  pile  is 
preferably  in  the  shape  of  a  circular  disc.  The  material  in  this 
shape  is  divided  into  four  quarters.  Two  opposite  quarters  are 
removed,  taking  care  to  remove  all  dust.  The  remaining  quarters 
are  then  mixed  together.  After  mixing,  the  material  is  spread 
out  again,  as  before,  and  quartered  again.  This  process  is  followed 
until  the  quantity  remaining  is  of  the  size  required  for  the  ex- 
periment. 


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Report  on  Tests  for  Concrete  Materials.         475 

Tensile  or  Compressive  Test  of  Mortar. 

The  Committee  recommends  the  test  of  the  strength  of  mortar 
as  that  best  indicating  the  quality  of  the  fine  aggregate. 

To  eliminate  variations  in  result,  due  to  the  character  of  the 
cement,  the  difference  in  laboratory  conditions,  and  the  .personal 
equation  of  the  operator,  the  test  always  must  be  a  comparative 
one.  For  comparison,  standard  Ottawa  sand  which  is  used  for 
cement  tests,  and  which  every  well-equipped  laboratory  should 
be  provided  with,  is  recommended. 

The  Joint  Committee  on  Concrete  and  Reinforced  Concrete 
in  their  1908  report,  makes  the  following  recommendation  for  this 
test  of  strength : 

Mortars  composed  of  one  part  Portland  cement  and  three  parts  fine  aggre- 
gate by  weight  when  made  into  briquets  should  show  a  tensile  strength  of 
at  least  seventy  (70)  per  cent,  of  the  strength  of  1 : 3  mortar  of  the  same  con- 
sistency made  with  the  same  cement  and  standard  Ottawa  sand. 

While  this  requirement  is  far  in  advance  of  usual  practice, 
where  no  laboratory  tests  are  required,  it  is  not  so  severe  as 
should  now  be  demanded  in  the  present  state  of  the  art  of  rein- 
forced concrete  construction.  For  the  present,  the  Committee 
recommends  that  sand  used  in  reinforced  concrete  be  accepted 
only  after  tensile  or  compressive  tests  of  1  :  3  mortar  made  with 
the  sand  in  question,  in  comparison  with  similar  tests  of  mortar 
of  standard  sand  made  up  at  the  same  time  under  the  same 
conditions. 

The  Committee  is  not  yet  prepared  to  recommend  a  fixed 
value  for  the  ratio  of  strength  for  acceptance.  It  is  suggested 
for  the  present  that  the  ratio  be  set  to  suit  individual  requirements. 

To  avoid  the  removal  of  any  coating  on  the  grains  which 
may  affect  the  strength,  bank  sand  should  not  be  dried  before 
being  made  into  mortar,  but  should  contain  natural  moisture. 
The  percentage  of  moisture  to  use  for  correcting  the  weights  in 
measuring  the  proportions  may  be  determined  upon  a  separate 
sample.  From  10  to  40  per  cent,  more  water  may  be  required 
in  mixing  bank  sands  or  artificial  aggregates  than  for  standard 
Ottawa  sand  to  produce  the  same  consistency. 

In  the  mortar  tests,  enough  test  pieces  should  be  made  to 
test  at  72  hours,  7  days  and  28  days,  the  first  24  hours  all  being 
stored  in  moist  air,  maintained  at  a  temperature  of  70  deg.  Fahr., 


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476         Report  on  Tests  for  Concrete  Materials. 

and  the  remainder  of  the  period  in  water  at  the  same  tempera- 
ture. The  72-hour  test  is  the  mast  severe,  and  sand  failing 
to  attain  this  requirement  frequently  reaches  it  at  7  days  or  at 
28  days,  and  can  then  be  accepte^d.  If,  however,  the  72-hour 
briquets  break  in  the  clips  of  the  machine,  or  if  the  test  pieces 
at  this  age  show  very  low  strength,  say  25  per  cent,  or  less,  of 
the  strength  of  standard  sand  mortar,  the  sand  should  be  considered 
dangerous  to  use  on  any  important  work  of  construction. 

Mechanical  Analysis. 

For  proportioning  fine  and  coarse  aggregate,  the  tests  of 
mechanical  analysis  are  important.  Curves  of  mixtures  in  dif- 
ferent proportions,  based  on  the  combined  analyses  of  the  cement, 
fine  aggregate,  and  coarse  aggregate,  may  be  drawn  and  studied 
to  obtain  the  proportions  corresponding  most  nearly  to  the  ideal 
requirements.  The  proportions  thus  found  may  then  be  used 
in  tests  of  volume,  as  referred  to  below. 

Mechanical  analysis  of  fine  aggregate  is  valuable  as  furnish- 
ing an  indication  of  its  quality.  It  is  recommended  that  fineness 
requirements  be  introduced  into  concrete  specifications.  This 
test  cannot  be  relied  upon  fully,  however,  since  there  may  be 
impurities  in  the  sand  that  will  make  it  unfit  for  use  even  when 
the  analysis  is  satisfactory.  The  chemical  and  also  the  min- 
eralogical  composition  of  the  sand  also  may  afifect  its  strength. 
Leaving  out  of  consideration,  however,  the  question  of  impurities, 
for  which  specific  tests  probably  will  soon  be  evolved,  the  test 
of  mechanical  analysis,  or  granulometric  composition,  as  it  is 
sometimes  termed,  is  worthy  of  much  further  development. 
Laws  which  govern  the  effect  of  the  sizes  of  the  particles  of  the 
aggregate  upon  the  resulting  mortar  or  cement  are  not  yet  clearly 
formulated. 

Further  studies  are  necessary  for  the  selection  of  standard 
sieves  for  use  in  mechanical  analysis.  From  the  report  of  the 
Committee  on  Reinforced  Concrete  of  this  Association,*  the  fol- 
lowing paragraphs  are  quoted: 

19.  The  relative  strength  of  mortars  from  different  sands  is  largely 
affected  by  the  size  of  the  grains.  A  coarse  sand  gives  a  stronger  mortar 
than  a  fine  one,  and  generally  a  gradation  of  grains  from  fine  to  coarse  is 

♦  See  ProeeedingM,  Vol.  V,  p.  457.  —  Ed. 


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Report  on  Tests  for  Concrete  Materials, 


477 


advantageous.  If  a  sand  is  so  fine  that  more  than  10  per  cent,  of  the  total 
dry  weight  passes  a  No.  100  sieve,  that  is,  a  sieve  having  100  meshes  to  the 
linear  inch,  or  if  more  than  35  per  cent,  of  the  total  dry  weight  passes  a  sieve 
having  50  meshes  per  linear  inch,  it  should  be  rejected  or  used  with  a  large 
excess  of  cement. 

20.  For  the  purpose  of  comparing  the  quality  of  different  sands  a  test 
of  the  mechanical  analysis  or  granulometric  composition  is  recommended, 
although  this  should  not  be  substituted  for  the  strength  test.  The  percentages 
of  the  total  weight  passing  each  sieve  should  be  recorded.  For  this  test  the 
following  sieves  are  recommended:* 

0.250  inch  diameter  holes,  t 

No.      8  mesh,  holes  0.0955  inch  width  No.  23  wire. 
No.    20       "        "    0.0335     "  "  No.  28      " 

No.    50       "        "    0.0110     "  "  No.  35      " 

No.  100       "        "    0.0055     "  "  No.  40      " 

21.  The  effect  of  mechanical  analysis  or  granulometric  composition 
upon  the  strength  of  mortar  is  illustrated  in  Appendix.  By  this  table  (which 
follows)  the  relative  strength  of  different  sands  may  be  approximately  estimated. 


TssTs  BY  New  York  Board  of  Water  Supply  of  1:3  Mortar 
Made  with  Sands  of  Different  Mechanical  Analysis. 


Peroentaces  Paadns  Sioves. 

Tenmle  Testa. 

CompreasioD  Test. 

No.  4.      1    No.  8. 

No.  50. 

No.    100. 

7  days. 

00  days. 

7  days. 

90  days. 

100      '       70 

12 

5 

213 

613 

2690 

5640 

100 

86 

21 

6 

263 

412 

1915 

4660 

100 

99 

26 

2 

177 

325 

905 

2170 

100 

97 

28 

6 

178 

282 

1070 

1500 

100 

94 

44 

12 

139 

228 

905 

1130 

100 

100 

52 

14 

122 

170 

275 

810 

100 

100 

94 

48 

80 

149 

330 

490 

Void  Tests. 

Void  tests  of  coarse  aggregates  frequently  are  used  to  de- 
termine proportions  for  concrete.  They  do  not  give  entirely 
correct  results,  however,  unless  the  tests  are  made  with  mixtures 


*  Sheet  brass  periorated  with  round  holes  passes  the  material  more  quickly  than  square 
Round  holes  corresponding  to  sieves  No.  8,  20  and  50  respectively  are  approximately 
0.13&,  0.060, 0.020  inch  diameter. 

t  A  No.  4  sieve,  having  4  meshes  per  linear  inch,  passes  approximately  the  same  sise 
gnUns  as  a  sieve  with  0.25  in.  diameter  holes. 


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478         Report  on  Tests  for  Concrete  Materials. 

of  all  the  ingredients.  Usually  some  of  the  grains  of  the  fine 
aggregate  are  so  coarse  as  to  force  apart  the  grains  of  the  coarse 
aggregate.  If  the  sand  is  fine  in  proportion  to  the  stone,  less 
mortar  will  fill  the  voids  of  the  stone  than  if  the  sand  is  coarser 
and  therefore  more  nearly  the  size  of  the  stone  particles. 

Void  tests  of  fine  aggregate  are  also  affected  by  the  fact 
that  the  cement  forces  the  grains  of  sand  apart.  The  voids  in 
fine  aggregate  also  are  affected  to  a  large  degree  by  the  percentage 
of  moisture  contained  in  it.  If  perfectly  dry,  a  fine  aggregate 
with  grains  of  uniform  size  may  have  nearly  the  same  percentage 
of  voids  as  a  coarse  aggregate  of  uniform  size  grains,  although 
the  former  will  produce  a  very  weak  mortar  and  the  latter  a 
strong  one.  If  the  voids  were  based  on  the  volume  of  the  moist 
aggregate,  the  results  would  be  more  normal,  but  a  slight  varia- 
tion in  the  percentage  of  moisture  produces  such  a  marked  effect 
that  it  is  impossible  to  make  true  comparisons  in  this  way. 

A  common  method  of  determining  the  voids  in  an  aggregate 
is  to  place  it  in  a  measure,  either  loose  or  compacted  as  desired, 
and  measure  the  quantity  of  water  which  can  be  poured  in.  The 
percentage  of  voids,  either  by  weight  or  volume,  is  thus  found 
directly.  This  method  with  a  clean  coarse  aggregate  is  fairly 
satisfactory.  With  a  fine  aggregate,  however,  air  is  entrained 
and  it  is  almost  impossible  to  obtain  correct  results. 

Another  plan  sometimes  followed  is  to  measure  the  material ; 
place  a  definite  quantity  of  water  in  a  graduated  vessel ;  pour  the 
aggregate  into  the  water;  and  determine  from  the  graduated 
scale  the  difference  in  volume  of  the  water  before  and  after  add- 
ing the  aggregate.  This  difference  is  the  amount  of  water  which 
the  aggregate  displaces.  This  is  substantially  a  specific  gravity 
method. 

A  still  simpler  plan,  if  the  specific  gravity  of  the  aggregate 
is  known  or  can  be  readily  determined,  is  to  weigh  a  given  bulk 
of  the  aggregate,  loose  or  compacted  as  required,  correct  for 
moisture,  and  compute  the  voids  directly. 

Weight. 

Weight  tests  have  the  same  limitation  as  void  tests,  since 
the  weight  is  affected  by  the  percentage  of  moisture  contained 
in  the  aggregate.     The  weight  also  varies  directly  with  the  specific 


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Report  on  Tests  for  Concrete  Materials.  479 

gravity.  If  the  specific  gravity  of  the  material  is  known  and  the 
percentage  of  moisture  is  determined,  the  voids  can  be  computed, 
as  indicated  above. 

Volumetric  Tests  op  Mortar  of  Fine  Aggregates. 

If  there  are  no  organic,  or  other  similar  impurities,  that  ab- 
normally reduce  the  strength,  the  aggregate  producing,  with  the 
cement  and  mortar,  the  smallest  volume  of  mortar  or  concrete 
is  apt  to  give  the  greatest  strength. 

A  volumetric  test  is  better  than  an  ordinary  void  or  a  weight 
test  because  the  aggregate  is  mixed  with  cement  and  water  as 
in  practice. 

The  general  method  employed  in  making  a  test  of  volume 
is  to  mix  up  the  aggregates  in  the  given  proportions  by  weight, 
add  enough  water  to  produce  a  consistency  slightly  softer  than 
used  in  tensile  tests,  and  determine  the  bulk  of  mortar  or  con- 
crete made  with  this  mixture.  Knowing  the  specific  gravity  of 
all  the  materials  used,  the  absolute  volumes  and  density  can  be 
computed.  The  method  of  making  this  test  is  described  more 
fully  in  a  paper  on  Concrete  Aggregates  presented  in  1906.* 

Volumetric  Tests  of  Concrete  Ingredients  for 
Determining  Proportions. 

One  of  the  most  valuable  fimctions  for  volumetric  tests 
lies  in  determining  the  proportions  of  concrete.  The  value  of 
the  test  is  based  on  the  principle  that,  with  the  same  proportion 
of  cement,  the  mixture  which  gives  the  smallest  volume,  and  ia 
therefore  the  densest,  usually  produces  the  strongest  concrete. 
This  rule  is  not  strictly  true  for  permeability  because  the  size 
of  the  voids  as  well  as  the  density  influence  the  permeability. 

For  determining  the  density  of  the  concrete,  the  specific 
gravity  of  each  aggregate  must  be  known.  The  specific  gravity 
of  cement  may  be  assumed  as  3.10.  An  average  specific  gravity 
for  bank  sand  is  2.65. 

The  process  of  making  volumetric  tests  of  mixtures  of  coarse 
and  fine  aggregates  with  cement  is  similar  in  principle  to  the 
volumetric  test  of  mortar  described.     Larger  volumes  must  be 


♦  See  Proceedirtifa,  Vol.  II,  p.  27.— Ed. 


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480         Report  on  Tests  for  Concrete  Materials. 

used  and  it  is  sometimes  easier  to  fill  a  measure  of  given  size 
and  determine  the  amount  left  over  than  to  determine  the  bulk 
of  the  total  material.  A  blank  form  for  use  in  this  test  is  referred 
to  below. 

Microscopical  Examination. 

The  mineralogical  composition  of  a  fine  aggregate  may  fre- 
quently be  determined  approximately  by  an  examination  under  a 
microscope  or  magnifying  glass  of  high  power.  Quartz  can  be 
recognized  and  if  dirt  surrounds  and  adheres  to  the  grains  it  can 
be  seen. 

Chemical  Analysis. 

The  value  of  chemical  analysis  is  not  clearly  defined.  A 
quartz  sand  in  general  is  better  than  a  natural  sand  of  other 
composition,  chiefly  because  it  is  cleaner.  It  is  claimed  by  some 
that  the  amount  of  clay  material  in  the  aggregate  affects  the  sand 
in  other  ways  besides  increasing  the  amount  of  fine  material. 

The  effect  of  colloids  and  colloidal  action  remains  to  be 
studied. 

The  ignition  test  referred  to  below  is  really  a  chemical  test. 

Test  for  Organic  Matter. 

Experience  with  defective  concrete  indicates  that  the  quality 
of  a  sand  may  be  very  poor  through  a  minute  quantity  of  organic 
or  vegetable  matter  contained  in  it.  The  best  method  of  testing 
for  this  and  the  limitations  which  must  be  placed  upon  the  quan- 
tity are  not  yet  clearly  defined. 

A  method  of  test  was  suggested  several  years  ago  by  the 
Chairman  of  the  Committee  and  has  been  used  in  practice  by 
him  and  also,  more  recently  with  some  modifications,  by  another 
member  of  the  Committee,  Mr.  Chapman.  The  methods  are 
substantially  as  follows: 

Two  hundred  grams  of  the  damp  sand  just  as  it  is  received 
at  the  laboratory  are  weighed  out  and  put  into  a  jar  or  a  graduate. 
If  desired,  the  quantity  of  this  may  be  measured  and  a  given 
bulk,  such  as  100  c.  c,  may  be  used  instead  of  the  fixed  weight. 
If  thus  measured  by  volume  the  weight  is  also  determined.  Water 
is  added  and  the  mixture  is  shaken  violently  and  stirred  for  2 
minutes.     Then  the  dirty  water  is  poured  off  into  a  separate 


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Report  on  Tests  for  Concrete  Materials.         481 

vessel.  More  water  is  added  and  the  operation  is  repeated  until 
the  water  is  practically  clear.  The  water  poured  off  is  evapo- 
rated, taking  care  not  to  raise  the  temperature  much  above  the 
boiling  point,  or  else  by  another  method,  it  is  poured  through 
a  filter  paper  (previously  weighed)  and  this  residue,  together 
with  the  paper,  dried  at  a  temperature  of  212  deg.  Fahr.  The 
filter  paper  and  residue  are  then  weighed  together,  the  weight  of 
the  filter  paper  deducted,  and  the  remainder  is  considered  as 
silt.  The  percentage  is  recorded  which  the  weight  of  this  silt, 
or,  by  the  other  method,  the  weight  of  the  silt  left  from  the 
evaporated  water,  bears  to  the  weight  of  the  original  sand. 

The  evaporated  residue,  or  else  the  filter  paper  with  its 
residue,  are  ignited  in  a  crucible  at  a  red  heat,  and  the  loss  of 
weight  by  this  process  (after  allowing  for  the  weight  of  the  filter 
paper)  is  taken  to  indicate  the  amount  of  organic  or  vegetable 
matter.  The  percentage  of  this  is  expressed  both  in  terms  of 
the  silt  and  of  the  total  sand. 

Blank  Forms  for  Reports. 

Forms  are  appended  to  this  report  that  have  been  used  in 
laboratories  of  members  of  your  Committee  for  special  tests  of 
aggregates,  see  Figs.  1-4. 

Respectfully  submitted, 

Sanford  E.  Thompson,  Chairman, 
Cloyd  M.  Chapman, 
William  B.  Fuller, 
Russell  S.  Greenman, 
Arthur  N.  Talbot. 


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482 


Repobt  on  Tests  fob  Concrete  Materiaia. 


SANO  TEST  REPORT 


grJ^»Ji.M 


rijEAi^wjf 


FIG.    1. — BAND  TEST  REPORT   USED  BY   WBSTINGHOUSE,   CHURCH,   KERR 

AND   COMPANY.      CLOYD  M.   CHAPMAN,    ENGINEER  IN  CHARGE, 

NEW   YORK,   N.   Y. 


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Report  on  Tests  por  Concrete  Materials. 


483 


Contract  No. 


TESTS  OF  SAND  fpom bank  at ^ ,  N.  Y. 

Proposed  for  use  on  contract  No ,  Ree.  No Canal, Division..... 

Contract  sample  No taken ,  received  at  Laboratory ,  made  up 

Sand  is  maitUy  quartz  and  feldspar  with  some  hornbUnd  and  magnetite. 
Percentage  of  Voids,  36^;  Loam.  S.2;  Organic  matter,  trace. 
Parts  of  sand  to  cement,  by  bulk: — S  sand  to  1  cement. 
Per  cent  water  used  -\-13. 

Cement  used  in  tests . 

For  test  of  cement  see  Vol.      ,  Page 
Temperature,  Fah.  when  mixed,  Air  ,  Water 

Briquettes  kept  in  air  24  hours  and  then  inmiersed. 


TENSILE  STRENGTH  (in  pounda  per  square  inch) 


Natural  Sako 


I 


Washed  Sakd 


SIZE  OF  SAND 
Paisxno  Suyb 


Briquette'  _  . 
N©.        7  days 


178 
186 
192 
192 
170 


Total  I  918 
Average,    184 


28  daysl 

252  I' 

274  1 

2S0  \\ 
268 

260  ,| 


Briauette 


1294 
269 


Total 
Average 


7  days  l28  days, 
182    !    286 


196 
190 
198 
196 


962 
192 


276 
264 
262 
274 


I    No. 

I 

'  6(1/ 
]10 

130 


Per     H 
cent. 

100.0  \ 
lOO.Tl 
99.2  \ 
97.6  \ 
87.0  \\ 
68.0  \\ 


No. 

40 

60 

74 

100 

140 

200 


I  Per 

I  cent. 

I  SS.2 

I  16.0 


7.8 
3.2 
2.0 
14 


,  Reported  19    . 

I  Examined  and  Approved 

1362  1 1  Resident  Engineer. 

270  11  Accepted    .      Rejected. 


Tests  for  strength  made  by 
Tests  of  sand  made  by 


.    Recorded  by 


FiQ.  2. — Report  Card  of  Sand  Test  New  York  State  Testtno  Labor- 
ATORT,  Albany,  N.  Y.,  Russell  S.  Greenman,  Resident  Engineer 
IN  Charge  of  Tests. 


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484         Report  on  Tests  for  Concrete  Materials. 


SANFORD  E.  THOMPSON.  FUb,  8WBS. 

CoNBUiA'iNa  Enoinbbr,  Date,  Feb.  18, 1911. 

Newton  Highlands,  Mass.  Volumetrie  or  Density  Teet.  Experimentor,  W.  O.  L 


(  1)  Test  Number ? V-e39 

(  2)  Date S/W/ll 

By  volume  1:2:4 

(  3)  Nominal  mix By  weight  1:1.8:S.8 

(  4)  Brand  of  cement 

(  5)  Weight  of  cement 2.000 

(  6)  Weight  of  aggregate  parsing  a  No.  100  sieve 0.0007 

(7)        '^       "         "         coarstt' than  a  No.  100  sieve 11.180 

(  8)         "        "  vessel  and  water  (before  using) 1 .600 

(9)  "       "      "       ''        "       (after  using) 0.740 

(10)  "        •*  water  used 0.760 

(11)  Total  weight  mixed  (5) +  (6) +  (7) +(10) 1S.947 

(12)  Weight  of  trav+tools       (aft«r  mixing) 2.760 

<13)         "        "    ''    +  "  (before  mixing) 2.626 

(14)  Weight  of  mixed  adhering 0.126 

(16)  Weight  of  waste+water 0.126 

(16)  Weight  of  waste 0.094 

(17)  Weight  of  free  water O.OSl 

(18)  Net  mix  of  set  =  (11) -(14) -(17) 18.791 

(19)  Water  left  on  tray  -^5J!^-(|y^^ior ^  ^^ 

(20)  Net  water  set  =  (10) -(17) -(19) 0.696 

(5)X(14) 

(21)  Net  cement  (5)"  (5)^,(6)4- (10) ^ -^^^ 

(22)  Net  aggregate  passing  a  No.  100  Sieve  -  (6)  —  (K\A.{k\  XTim  0.0O67 

(23)  Depth  of  concrete  in  cylinder 0.44^ 

(24)  Volume  of  concrete  in  cylinder 0.0869 

(25)  Net  water  per  cu.  ft.  as  mixed  (10)  h-  (24) 8.760 

(26)  "         "       "  "  set  (20) -^  (24) 8.020 

(27)  Net  cement  per  cu.  ft.  as  set  (21)  ^  (24) 22.000 

(28)  Net  aggregate  per  cu.  ft.  as  set  (22) -f  [(7)  -f-  (24)] 128.60 

(29)  Abs.  vol.  of  water  per  cu.  ft.  as  set  (26)  -^62.3 0.1286 

(30)  Abs.  vol.  of  cement  (27)  ^62.3 0.11S9 

(31)  Abs.  vol.  of  aggregate  (28)  -^^^.5 0.760 

(32)  Abs.  vol.  total* (29) +  (30) +  (31) / .0024 

(33)  Weight  of  form  +concrete 19.000 

(34)  "        "     "    6.166 

(35)  "        "  concrete 13.844 

(36)  Temperature  of  water 70'*F-. 

(37)  Time  of  mixing 10,00  a.m. 

(38)  Remarks  on  consistency JeUy  like 


Pig.   3. — Mechanical  Analysis  Report,   Sanford  E.   Thompson,   Con- 
sulting Engineer,  Newton  Highlands,  Mass. 


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Report  on  Tests  for  Concrete  Materials. 


485 


8ANFORD  E.  THOMPSON,  FUe,  8WBE. 

CoNBULTiNa  Enoxnesb,  Date,  Jan.  £4$  1911. 

Newton  Highlanda,  Mam.  Mechanical  Analysts.  Experimenter,  W.  E.  S. 

Test  made  for SWBE, 

Description Gravel  from  Neponsel  River. 

Samples  Taken  (date) Jan.  23 ^  1911,    Shipped  to  laboratory  in  bag. 

Samples  Received  (date) Jan.  24,  1911, 

Weight  Total  Sample 20  lbs. 

Client's  Mark 

Laboratory  Mark A,  S.,  186  SWBE. 

Analysis  No A.  S.  186. 

Per  cent.  Moisture 1.6% 


Sise  of  Sieve 

Total 

Totol 

Per 
cent. 

Totol 

Totol 

Per 
cent. 

Total 

Total 

Inches 

No. 

Weight 
PasSng 

Per  cent. 
Passing 

Finer 
than  H" 

2.50 

H 
1 
J 

J 

6 
12 
20 
40 
50 

100 

200 

1 

2.00 

1.60 

998.0 

677.2 

669.0 

388.0 

366.0 

160.6 

64.2 

17.0 

11.8 

6.8 

3.6 

100.0% 
67.8 
57.1 
38.9 
36.6 
16.1 

6.4 
1.7 
1.2 
0.6 
0.36 

1.00 

0.50 

....  j ...  . 

0.25 

100.0% 
94.3 
38.8 
16.6 

4.4 

3.1 
1.6 
0.9 

1 

0.16 

1 

0.0583 

0.0335 

.  .  . 

0.0148 

.... 

0.0110 

0.0055 

::::i:::: 

0.0030 

1 

Remarks 


Washing  No.  W226 
Tensile  No.  T926 
Report  made  Fe&.  1,  1911. 


Approved, 
Noted  by  S.E.T., 


Date  Initials 

Jan.  24,  1911.     W.  O.  L. 
Jan.  28,  1911.    S.  E.  T. 


Fig.  4. — ^Volumbtrig  or  Density  Report. 


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AGGREGATES  FOR  CONCRETE. 
By  William  M.  Kinney.* 

Within  the  past  few  years  has  been  seen  the  almost  universal 
adoption  of  the  Standard  Specifications  for  Portland  Cement  f  of 
the  American  Society  for  Testing  Materials.  Practically  all 
cement  made  in  this  country  is  guaranteed  to  meet  these  require- 
ments and  it  is  only  occasionally  that  a  shipment  fails  to  pass  the 
specifications  by  a  safe  margin.  Despite  the  precautions  taken  in 
the  making  and  testing  of  cement,  however,  there  are  occasionally 
complete  or  partial  failures  of  concrete  work.  Fortimately  these 
failures  usually  occur  during  the  process  of  construction  so  that 
the  loss  of  life  and  property  is  relatively  small,  but  that  there 
should  be  any  loss  whatever  in  this  type  of  construction  should 
lead  such  bodies  as  this  Association  to  strive  for  greater  efficiency 
by  a  careful  and  thorough  study  of  the  materials  entering  into 
and  the  workmanship  required  for  concrete. 

It  is  seldom  possible  to  determine  positively  the  cause  for 
such  failures;  in  fact,  the  number  of  reasons  given  for  a  particular 
failure  usually  varies  with  the  number  of  engineers  employed  on 
'  the  investigation.  It  is  essential,  therefore,  that  in  the  construc- 
tion of  any  concrete  or  reinforced  concrete  structure,  that  each 
step  be  made  with  absolute  surety  in  order  to  attain  success. 

Deficient  strength  in  concrete  is  usually  due  to  one  or  more 
of  the  following  causes:  poor  workmanship,  unsatisfactory 
aggregate  and  unfavorable  weather  conditions,  assuming  of  course 
that  the  design  is  right  and  that  the  cement  had  been  carefully 
tested  to  the  standard  specifications.  Poor  workmanship  can  be 
eliminated  from  this  discussion,  because  with  the  widespread 
distribution  of  literature  on  the  mixing  and  placing  of  concrete, 
it  should  be  possible  for  any  contractor  or  user  to  handle  concrete 
in  such  a  manner  that  success  will  be  assured.  However,  the 
question  of  aggregate  and  temperature  conditions,  with  usually 
a  combination  of  the  two,  is  a  matter  deserving  of  very  careful 
consideration.     Of  these  two,  the  question  of  aggregates  is  the 

*  Assistant  Inspecting  Engineer,  Universal  Portland  Cement  Company.  Pittsburgh,  Pa. 
t  Standard  No.  1.  National  Assooiation  of  Cement  Users. — Ed. 

(486) 


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Kinney  on  Aggregates  for  Concrete.  487 

paramount  issue,  as  it  is  almost  a  certainty  that  if  good,  clean 
aggregates  were  used,  at  least  three-fourths  of  the  frozen  concrete 
would  be  eliminated.  The  reason  for  making  this  statement  is 
based  upon  the  fact  that  when  concrete  is  subjected  to  actual 
freezing  weather  during  the  early  stages  of  hardening,  it  is  usually 
well  protected  and  poor  work  seldom  results;  but  when  it  is 
deposited  at  a  temperature  above  freezing  it  is  not  protected,  and 
owing  to  delay  in  hardening  due  to  unsatisfactory  aggregates, 
freezing  may  occur  the  following  night  or  even  a  number  of 
days  later.  It  is  certain  that  in  a  great  many  cases  had  clean 
aggregates  been  used  the  concrete  would  have  hardened  suffi- 
ciently during  the  favorable  weather  to  have  withstood  the  sub- 
sequent freezing  without  resultant  injury  to  the  concrete. 

The  aggregates,  therefore,  play  an  important,  if  not  the  most 
important  part  in  concrete  work,  and  are  without  doubt  subject 
to  the  greatest  variation,  yet  have  received  up  until  the  present 
time  the  least  study  of  all  the  adjuncts  of  good  concrete.  To  be 
sure,  there  are  the  studies  of  Feret,  Candlot  and  other  European 
experts.  Likewise,  the  Structural  Material  Division  of  the 
United  States  Geological  Survey  (now  under  the  Bureau  of 
Standards)  and  individual  investigators,  such  as  Thompson, 
Spackman  and  Greenman  have  given  valuable  information 
obtained  from  their  study  of  sand,  gravel  and  other  aggregates. 
This  work,  however,  has  of  necessity  been  limited  somewhat  to 
the  study  of  deposits  local  to  the  various  laboratories,  and  the 
results  are  chiefly  valuable  in  giving  an  idea  of  the  most  advan- 
tageous tests  for  detecting  the  properties  of  a  particular  aggregate, 
which  render  it  good  or  poor  for  concrete.  It  remains  to  apply 
these  tests  in  the  study  of  the  aggregates  being  used  or  proposed 
for  use  in  individual  structures  or  in  particular  localities. 

The  report  of  the  Committee  on  Specifications  and  Methods 
of  Tests  for  Concrete  Materials  has  been  presented.  It  would 
seem  highly  proper  for  this  committee  at  the  earliest  possible 
date  to  confer  the  committees  on  Concrete  and  Reinforced  Con- 
crete of  the  American  Society  for  Testing  Materials,  American 
Society  of  Civil  Engineers,  and  Association  of  American  Portland 
Cement  Manufacturers,  looking  toward  the  establishment  of  a 
standard  set  of  tests  for  concrete  materials.  Having  outlined  such 
methods,  it  should  then  be  within  the  power  of  this  committee  to 


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488  Kinney  on  Aggregates  for  Concrete. 

influence  the  various  Government,  State  and  commercial  bodies 
interested  in  this  subject  to  inaugurate  at  once  an  extensive  study 
of  these  materials  by  the  methods  outlined. 

The  magnitude  of  such  an  investigation  may  lead  to  the 
thought  that  it  is  not  feasible,  but  there  is  no  reason  why,  if 
properly  organized  under  an  advisory  board  composed  of  rep- 
resentatives of  the  various  large  engineering  societies,  the  work 
cannot  be  systematically  done  without  duplication  of  tests  by  the 
Bureau  of  Standards  and  the  various  State  Universities  and 
Experiment  Stations  together  with  whatever  assistance  may  be 
rendered  by  other  laboratories  of  a  public  or  private  nature. 

In  1905  there  was  established  at  St.  Louis  a  laboratory  under 
the  Structural  Materials  Division  of  the  United  States  Geological 
Survey,  which  published  in  1908  Bulletin  331  on  Portland  Cement 
Mortars  and  Their  Constituent  Materials,  Neither  this  laboratory 
nor  its  successor  in  this  line  of  work,  the  Bureau  of  Standards, 
has  given  any  further  data  on  this  very  important  subject.  It 
is  to  be  hoped  that  the  Bureau  of  Standards  will  continue  this 
very  necessary  work,  as  it  would  be  unfortunate  to  lose  the  prac- 
tical information  gained  by  the  investigators  in  conducting  the 
j&rst  series  of  tests.  Good  work  has  also  been  done  in  several  of 
the  State  Universities  and  Experiment  Stations.  It  is  pleasing 
to  note  that  the  University  of  Wisconsin  is  to  start  at  once  under 
Mr.  M.  0.  Withey,  a  comprehensive  study  of  the  aggregates  of 
Wisconsin.  If  Wisconsin  can  do  this,  why  cannot  other  States 
be  interested  in  a  similar  investigation? 

Such  an  investigation  will  not  by  any  means  solve  the  prob- 
lem and  insure  good  work  in  the  future,  but  it  will  give  an  idea 
of  the  relative  merits  of  the  various  aggregates  available  for  con- 
crete in  any  particular  locality.  This  in  itself  will  be  a  most 
important  step  forward,  as  it  is  safe  to  say  that  less  than  half  of 
the  architects  and  engineers  in  this  country  know  the  crushing 
strength  that  can  be  obtained  from  the  mixtures  they  specify 
with  the  aggregates  that  are  being  used  on  jobs  under  their  super- 
vision every  day. 

This  statement  was  recently  borne  out  by  an  investigation  of 
the  aggregates  available  for  concrete  in  one  of  our  larger  cities 
prior  to  the  formation  of  a  Building  Code  for  concrete  and  rein- 
forced concrete  buildings.     In  this  code  it  was  originally  planned 


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Kinney  on  Aggregates  for  Concrete. 


489 


to  have  the  requirement  for  compressive  strength  of  1:2:4  con- 
crete at  28  days  at  least  2400  lb.  per  sq.  in.  This  was  later 
reduced  to  2000  lb.  and  the  allowable  stresses  figured  accord- 
ingly. An  investigation  by  the  writer  and  others  interested  in 
the  writing  of  the  Code  developed  the  fact  that  though  the  supply 
of  sand  and  gravel  was  limited  to  practically  one  source  and  the 
crushed  stone  to  several  quarries  in  the  same  vein,  very  few  tests 
on  the  aggregate  were  obtainable  and  these  seemed  to  indicate 
that  even  2000  lb.  was  too  high.  A  series  of  tests  was  started 
and  the  results  to  date  are  quite  surprising.     The  specifications 

Table  I. — Comparative  Compressive  Strength  in  lb.  per  sq.  in.  of 
Concrete  Made  from  Various  Aggregates. 


Mark. 

7  Days. 

Ordinary  gravel.. 
Large  gravel 

Stone 

677 
o9o 
603 

626 

898 
677 

874 

816 

819 
858 

962 

879 

28  Days. 

3Mos. 

1578 
1390 
1633 

1512 
1673 
1943 

1533 

1709 

1626 
1640 

1684 
1779 

1580 

1649 

1582 

1704 

1824 
1972 


1880 
1888 


2031 
2206 


2484 
2240 


Proportions. 


1  part  typical  cement. 

2  parts  nver  sand  passing  */u  in.  screen, 
'cl  Vw  in.  '    "'   ' 


4  parts  river  gravel 


.  to  V«  in. 


1  part  tsrpical  cement. 

2  parts  nver  sand — 3  parts  through  Vi« 

in.  screen,  1  part  Vi«  in.  to  1/4  in. 
4  iMtrts  river  gravel  1/4  in  to  1  in. 


1  part  typical  cement. 

2  parts  nver  sand — 3  parts  throujgh  */i« 

in.  screen,  1  jmrt  '/is  in.  to  1/4  in. 
4  IMtrts  crushed  stone  1/4  in.  to  1  in. 


Typical  cement  used  was  a  mixture  of  five  brands.  Medium  consist- 
ency. Hand  mixed.  Test  pieces  8  in.  in  diameter  and  16  in.  long.  Aged 
in  temperature  of  about  70^  F.  and  protected  from  drying  out  by  cotton  bags 
wet  twice  a  day. 

require  that  the  coarse  aggregate  shall  pass  a  1-in.  ring  and  be 
retained  on  a  i-in.  ring;  fine  aggregate  to  be  all  that  passing  a 
i-in.  ring.  The  material  produced  commercially  was  being 
screened  through  a  |-in.  and  over  a  A-in.  mesh,  so  that  tests  were 
made  on  the  aggregates  as  conmiercially  produced  and  on  samples 
specially  prepared  to  meet  the  specifications.  In  the  case  of  the 
sand,  this  was  done  by  mixing  with  three  parts  of  sand  passing  a 
^-in.  screen,  one  part  of  the  fine  material  passing  a  J-in.  screen 
obtained  from  the  i^-in.  to  f-in.  gravel.  The  results  up  to  three 
months  are  shown  in  Table  I  and  prove  conclusively  that  with 


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490 


Kinney  on  Aggregates  fob  Concrete. 


Tabub  II.— Tests  on  Typical  Ceiibnt  used  in  Coiipbessiqn  Tests. 

Fineness  100  mesh — 94.8  per  cent.        Initial  Set — 4  Hours. 

Fineness  200  mesh— 77.4  per  cent.        Final  Set— 7  Hours  25  Minutes. 

Soundness — Satisfactory.  Normal  Consistency — 24  per  cent. 

Chemical  Analysis. 

Silica 20.72 

Alumina 7.24 

Iron  Oxide 2.84 

Caleium  (hdde 62.85 

Magnesia 2.47 

Sulphuric  Anhydride 1 .  42 

Moisture  and  undetermined 2 .  46 

Tensile  Strength  in  lb.  per  sq.  in. 


NeM. 

1  :  3  Ottawa  Sand. 

24  Houni. 

7  Days. 

28  Days. 

3  Months. 

3  Days. 

7  Days.     |  28  Days. 

3  Months. 

310 
815 
330 

600 
660 
660 

740 
780 
750 

765 
775 

740 

180 
190 
200 

340 
300 
300 

420 
390 
400 

440 
480 
460 

318 

640 

757 

760 

190 

313 

403 

460 

I  : 

3  Commeroial  Sand. 

3  parts  throi 

7  Days. 

28  Days. 

3  Months. 

7  Days. 

240 
300 
265 

268 

390 
380 
36.^ 

378 

390 
425 
380 

39S 

290 
340 
290 

307 

1  :  3  Special  Sand. 


28  Days. 


460 
420 
400 

427 


3  Months. 


505 
480 
535 

506 


Granulombtric  Analysis. 


Commercial 
Sand. 

'^t» 

P«r  fwnt  retained  on  No.      4  mcvh . .  t . . . . . .  t . . . .  t  -  - ,  - 1  -  -  - 

0 
10.6 
19.2 
25.8 
11.8 

5.8 
24.4 

0.6 

1.4 

0 

10      **    

31.5 

20      '•    

14.5 

30      •*    

15  2 

40      "    

10.5 

50      "    

4.2 

80      '*    

18.5 

100      "    

2.3 

Through  100      " 

3.2 

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Kinney  on  Aggregates  for  Concrete. 


491 


such  proportions  a  requirement  of  2000  lb.  per  sq.  in.  is  too  hi|^ 
for  the  local  material,  and  that  either  the  amount  of  cement  will 
have  to  be  increased  or  the  proportions  readjusted  so  as  to  pro- 
duce higher  results.  In  these  tests,  which  were  made  on  8-in. 
diameter  cylinders  16  in.  long,  the  concrete  was  accurately  pro- 
portioned and  mixed  by  hand  and  the  test  pieces  were  stored  in 
an  even  temperatiu-e  approximating  70*  F.,  being  protected  from 

Table   III. — Compressive  Strength  in  lb.  per  sq.  in.   of  Concrete 
CTLifn)ERS  Using  Material  from  Same  Source  as  Table  I. 


Brand  of  Cement. 


10  Days. 

4«6 
498 
600 

521 

439 
539 
409 

462 

620 
527 
515 

520 

395 
521 
536 

484 

430 
396 
434 

420 


30  Days. 

3  Months. 

803 

960 
828 

Ill 

893 

1275 

990 
904 
800 

1182 
1096 
1018 

898 

1098 

820 

999 

1142 

1433 
1172 
1136 

987 

1247 

774 

872 
898 

1138 
1263 
1316 

848 

1235 

706 
834 
1084 

1263 
1219 
1160 

878 

1214 

6  Months. 


looa 

1185 
1131 

1106 

1152 
1063 
1299 

1171 

1333 

949 

1464 

1248 

1084 
1382 
1609 

1358 

1060 
1064 
1046 

1063 


Proportions:  1  part  cement  (5  brands  used  individually),  2}  parts  river 
sand  through  A  in.,  5  parts  river  gravel  A  »n.  to  li  in. 

Test  pieces  8  in.  in  diameter  and  16  in.  long,  mixed  with  batch  mixer, 
stored  in  open  shed  and  sprinkled  night  and  morning  for  first  7  days. 

drying  out  by  cotton  bags  wet  twice  a  day.  The  cement  used 
was  a  mixture  of  five  representative  brands,  the  results  of  tests 
on  which  are  shown  in  Table  II.  In  the  same  table  are  granulo- 
metric  and  tensile  tests  on  the  commercial  and  special  sand.  It 
will  be  noted  that  despite  the  fact  that  the  commercial  sand 
approximates  very  closely  the  tensile  strength  of  Ottawa  sand  and 
the  special  sand  exceeds  in  strength  that  of  Ottawa  sand,  yet 


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492 


Kinney  on  Aggregates  for  Concrete. 


used  in  concrete  with  gravel  from  the  same  source  and  a  very 
good  grade  of  crushed  stone,  neither  of  these  materials  developed 
a  crushing  strength  of  2000  lb.  per  sq.  in.  at  28  days.    Other 


Table  IV. — Comparative  Cold  Weather  Tests  on  (8  in.  Diameter  by 

16  IN.  Long)  Cylinders  Mixed  1  Cement,  2i  Sand,  5  Gravel, 

December  4,  1911.    Cyunders  Protected  from  Frost  by 

Cotton  Bags.    Hand  Mixed,  Medium  Consistency. 

Crushiiig  Strength  in  lb.  per  sq.  in. 


Age. 


3  days  in  air  and  1  day  in  laboratory . 


7  days  in  air. 


14  days  in  air. 


30  days  in  air. 


Brand  "A" 


116 
122 

119  Average 

227 
265 

246 


4S4 
458 


471 


640 
739 


689 


Brand  "B" 


95 
95 

95  Averago 

199 
209 

205 

440 

388 

414 

495 
653 

574 


Temperature — Degrees  Fahrenheit. 


Ist  day 

2d  " 

3d  " 

4th  " 

5th  '• 

6th  " 

7th  •• 

8th  *• 

9th  •• 

10th  '• 

11th  " 

12th  " 

13th  " 

14th  " 

15th  " 


Max. 


30 
36 
48 
54 
54 
54 
66 
61 
59 
51 
42 
47 
58 
38 
33 


Min. 


18 
21 
27 
29 
40 
48 
46 
58 
45 
35 
32 
39 
38 
32 
30 


Mean. 


24 
28 
38 
42 
47 
51 
56 
60 
52 
43 
37 
43 
48 
35 
32 


16th  day. 
17th    ■ 
18th 
19th 
20th 

2l8t 

22d 
23d 
24th 
25th 
26th 
27th 
28th 
29th 
30th 


Max. 

Min. 

Mean. 

34 

28 

31 

41 

24 

32 

49 

36 

42 

52 

44 

48 

47 

33 

40 

39 

33 

36 

45 

34 

40 

56 

40 

48 

67 

23 

40 

23 

14 

18 

32 

18 

25 

45 

32 

38 

64 

28 

41 

29 

26 

28 

34 

23 

28 

results  obtained  on  material  from  the  same  source  are  shown 
Tables  III  and  IV,  and  the  latter  table  particularly  shows^that 
this  aggregate  is  poor  for  cold  weather  work.  Great  care'should 
be  exercised  in  the  use  of  such  material  in  the  winter  time  as 


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unless  the  materials  are  heated  and  the  concrete  well  protected, 
poor  results  are  almost  inevitable. 

Having  established  the  value  of  aggregates  obtained  from 
any  particular  soiu-ce,  it  is  then  necessary  to  see  that  the  mate- 
rials received  on  the  job  are  equal  in  quality  to  the  samples 
tested.  An  examination  of  the  bank,  pit  or  quarry  may  often 
reveal  the  fact  that  it  would  be  impossible  to  obtain  a  uniform 
product.  In  such  cases,  extreme  care  must  be  exercised  by  the 
men  obtaining  the  material  and  frequent  tests  should  be  made 
to  see  that  that  received  is  right. 

The  pier  shown  in  Fig.  1  is  a  good  illustration  of  the  effect  of 
variation  in  aggregate.  This  pier  was  built  in  connection  with 
two  abutments  to  support  a  steel  girder  railroad  bridge  across  a 
small  stream.  Prior  to  starting  the  concrete  work  the  engineer 
secured  a  sample  of  the  sand  and  gravel  which  the  contractor 
proposed  to  use,  and  the  laboratory  results  obtained  indicated 
that  the  materials  as  sampled  were  entirely  satisfactory  for  con- 
crete work.  That  the  material  as  received  was  not  good,  and 
apparently  not  equal  to  the  sample,  is  evidenced  by  examination 
of  the  condition  of  the  concrete.  A  photograph  of  the  gravel 
bank  (Fig.  2)  reveals  the  seat  of  the  trouble.  The  dark  streaks 
are  apparently  decayed  vegetable  matter,  while  here  and  there 
through  the  bank  will  be  noticed  strata  of  very  fine  uniform  size 
sand.  Examination  of  such  a  bank  indicates  quite  conclusively 
that  the  aggregate  could  not  rim  uniformly,  and  imdoubtedly  the 
delay  in  hardening  which  finally  resulted  in  freezing  was  due  to 
the  presence  of  too  much  fine  sand  and  loam.  That  this  was 
the  cause  of  the  trouble  is  conclusively  proven  by  the  fact  that 
the  poorest  results  are  evidenced  at  the  water  level  where  the 
fine  material  held  the  moisture  and  at  the  end  of  a  day's  work 
about  midway  of  the  pier  where  most  of  the  fine  material  floated 
to  the  top  of  the  concrete. 

On  another  job  of  a  similar  nature,  but  involving  the  use  of 
approximately  50,000  barrels  of  cement,  the  results  were  anal- 
ogous. A  large  amount  of  concrete  was  condemned  on  account 
of  imsatisfactory  strength.  In  the  middle  of  a  1000-yd.  founda- 
tion laitance  was  found  over  a  foot  thick  which  had  the  appear- 
ance of  wet  clay  and  could  be  readily  dug  out  with  a  knife  even 
though  the  concrete  had  been  in  a  month.    Run-of-pit  gravel  was 


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being  used  which  had  been  tested  for  percentage  of  fine  and 
coarse  material  and  found  satisfactory,  but  examination  of  the 
pit  revealed  the  fact  that  it  would  have  been  impossible  to  have 
secured  a  sample  which  would  have  fairly  represented  the  deposit. 


Fia.    1. — DISINTEGRATED    CONCRETE    PIER,    DUE   TO    POOR    AGGREGATES. 

In  some  places  there  was  very  little  sand,  while  in  others  there 
was  practically  no  gravel.  As  a  mixture  of  one  part  cement  and 
seven  parts  run-of-pit  gravel  was  being  used,  the  natural  result 
of  the  use  of  the  latter  material  can  be  imagined.     Further  than 


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495 


this,  there  were  strata  of  very  fine  sandy  loam  throughout  the  pit 
and  the  large  section  of  laitance  was  the  result. 

The  foregoing  are  a  few  of  the  many  examples  which  can  be 
cited  where  failure  to  appreciate  the  value  of  .having  good 
aggregate  has  led  to  trouble  and  such  examples  emphasize  the 
importance  of  tests  of  the  aggregates.  It  is  quite  surprising  to 
find  architects  and  engineers  basing  their  designs  on  a  certain 
strength  of  concrete  which  cannot  be  obtained  or  may  be  largely 


FIG.  2. — GRAVEL  BANK  FROM  WHICH  POOR  AGGREGATE  WAS  OBTAINS^. 

exceeded  in  actual  practice,  and  surely  our  work  is  devoid  of  the 
fundamentals  of  good  engineering  when  we  use  without  ^scrim- 
ination  aggregates  of  high  and  low  strength  giving  values.  A 
more  thorough  study  of  our  sources  of  supply  for  concreting 
materials  and  a  more  careful  inspection  of  these  materials  as 
they  are  received  on  the  work,  is  of  utmost  importance  to  the  in- 
dustry and  it  should  be  one  of  the  first  efforts  of  this  Association 
to  study  this  important  subject. 

A  partial  bibliography  of  the  literature  on  aggregates  for  con- 


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496  Kinney  on  Aggregates  for  Concrete. 

Crete  is  given  below  with  the  hope  of  furthering  study  on  the 
subject. 

Concrete  Aggregates,  by  Sanford  E.  Thompson,  Proceedings  National 
Association  of  Cement  Users,  Volume  II,  p.  27.  See  also  Engineering  Record, 
January  27,  1906. 

Sands  and  Their  Relation  to  Mortar  and  Concrete,  by  Henry  S.  Spackman 
and  Robert  W.  Lesley.  Proceedings,  American  Society  for  Testing  Materials, 
Volume  VIII,  p.  429. 

The  Value  of  Sand  in  Concrete  Construction,  by  E.  S.  Larned,  Proceedings, 
National  Association  of  Cement  Users,  Volume  IV,  205. 

Concrete — Its  Constituent  Materials,  by  Russell  S.  Greenman,  Barge 
Canal  Bulletin  (New  York  State),  November,  1909,  p.  429. 

Practical  Tests  of  Sand  and  Gravel  Proposed  for  Use  in  Concrete,  by  Russell 
S.  Greenman,  Proceedings  American  Society  for  Testing  Materials,  Vol- 
ume XI,  p.  515.     See  also  Engineering  Record,  Volume  LXIV,  No.  3,  p.  66. 

Economical  Selection  and  Proportion  of  Aggregates  for  Portland  Cement 
Concrete,  by  Albert  A.  Moyer,  Engineering-Contracting,  Volume  XXXIII, 
No.  3,  p.  52. 

Concrete  Aggregates  by  Dr.  J.  S.  Owens,  Concrete  and  Corutrudional 
Engineering^  March  1909. 

\Portiand  Cement  Mortars  and  their  Constituent  Materials,  by  Richard  L. 
Hui|S)plhrey  and  William  Jordan,  Jr.,  BuUetin  331,  United  States  Geological 
Survey. 

Good  Concrete  and  How  to  Get  It,  by  F.  M.  Okey,  Municipal  Engineering, 
May,  1909. 

•  Notes  on  Concrete,  a  discussion  printed  in  Journal  of  Association  of  Engi- 
neering Societies.    See  Engineering  Record,  Volume  LXI,  No.  5,  p.  125. 

Impurities  in  Sand  for  Concrete,  a  discussion, — ^Transactions  American 
Society  of  Civil  Engineers,  September,  1909. 

BUist  Furnace  Slag  in  Concrete,  booklet  published  by  Carnegie  Steel  Com- 
pany, Pittsburgh,  Pa. 

Tests  t0  Determine  Effect  of  Mica  on  Strength  of  Concrete,  by  W.  N.  Willis, 
Engineering  News,  February  6,  1908. 

Directions  and  Suggestions  for  the  Inspection  of  Concrete  Materials,  by 
Jerome  Cochran,  Engineering-Contracting,  Volume  XXXVII,  No.  5,  p.  116. 

A  Study  of  Sand  for  Use  in  Cement  Mortar  and  Concrete,  by  E.  S.  Lamed, 
Journal  Association  of  Engineering  Societies,  Volume  XLVIII,  No.  4,  April, 
1912. 


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DISCUSSION. 


President  Humphrey. — The  relation  of  the  sand  to  the  Mr.  Humphrey, 
mortar,  especially  of  the  strength  of  mortars  made  of  the  com- 
mercial sand  to  that  of  mortars  of  standard  Ottawa  sand,  is  of 
interest.  There  has  been  a  great  deal  of  debate  in  the  Joint 
Committee  as  to  whether  they  should  show  the  same  strength 
or  possibly  less.  Engineers  from  New  England,  especially  from 
Boston,  object  to  requiring  the  same  strength,  because  in  their 
locality  it  is  impossible  to  obtain  a  sand  that  would  show  this 
strength,  therefore  making  the  requirement  a  hardship.  I  believe, 
however,  with  Mr.  Kinney,  taking  sand  the  country  over,  that  the 
various  sands  should  show  at  least  the  strength  of  the  Ottawa 
sand,  and  that  localities  where  it  is  not  possible  to  obtain  this 
strength  must  fix  the  requirement  to  suit  their  locality.  It  is 
certainly  a  fact  that  the  well  graded  sands  give  higher  results 
than  the  standard  Ottawa  sand.  The  standard  Ottawa  is  a  one 
size  sand  with  a  large  percentage  of  voids  and  the  strength  of 
the  mortar  in  which  it  is  used  is  less  than  that  of  sands  well 
graded. 

Mr.  Kinney  states  that  grading  gives  density  and  that  the 
increased  density  gives  an  increased  strength.  The  retaining 
walls  with  the  disintegrating  mortar  referred  to  are  as  fine  an 
example  of  cause  and  effect  as  could  possibly  be  had.  It  did  not 
require  a  technical  man  to  look  at  the  sand  bank  to  see  that  the 
material  was  not  suitable  for  mortar.  It  was  quite  evident  that 
the  fine  sand  in  the  mortar  retarded  the  hardening,  and  left  the 
mortar  with  insufficient  strength  and  thus  easily  damaged  by 
frost  action.  This  is  one  of  the  most  important  subjects  that  we 
can  discuss.  There  is  more  information  desired  and  great  need 
for  intelligent  understanding  of  just  what  important  part  sand 
plays  in  mortars  and  concrete;  it  probably  has  a  more  important 
bearing  on  the  resulting  strength  of  the  structure  than  the  strength 
of  the  cement.     I  think  we  are  more  prone  to  ascribe  the  defects 

(497) 


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498 


Discussion  on  Aggregates. 


Mr.  Kinney. 


Mr.  Wilson. 


Mr.  Httmphrey. 


in  mortar  or  concrete  directly  to  the  cement  rather  than  the  sand 
used. 

Mr.  Wm.  H.  Kinney. — The  sand  from  this  particular  bank 
had  been  tested  by  the  engineer  and  was  found  to  have  a  strength 
which  compared  favorably  with  Ottawa  sand.  In  fact,  it  passed 
the  70  per  cent  strength  requirement  by  a  very  satisfactory 
margin.  However,  the  samples  did  not  fairly  represent  the 
material  the  contractor  was  obtaining  from  the  bank. 

Mr.  Percy  H.  Wilson. — There  was  a  case  called  to  my 
attention  5  or  6  months  ago  where  a  railroad  engineer  endeavored 
to  obtain  in  the  laboratory  a  compressive  strength  of  2,000  lb. 
per  sq.  in.,  the  requirement  of  the  Joint  Committee.  On  obtaining 
only  about  1,800  lb.  the  test  was  tried  over  and  over,  varying 
the  aggregate,  but  the  strength  never  w^ent  up  to  2,000  lb.  Now 
is  this  requirement  of  the  Joint  Committee  too  high? 

President  Humphrey. — Many  contractors  and  probably 
a  good  many  engineers  and  architects  never  seem  to  think  it  is 
necessary  to  test  the  sand.  They  simply  pass  on  it  from  a  visual 
inspection,  whereas  the  committee  states  that  a  differentiation 
between  a  good  or  a  poor  sand  can  only  be  made  by  actual  test. 

I  would  say  I  do  not  think  the  standard  requirement  set  by 
the  Joint  Committee  of  2,000-lb.  concrete  is  too  high.  It  is  a 
standard  we  should  work  to.  Unfortunately  there  is  the  practice 
in  this  country  of  specifying  the  proportions  such  as  1  :  2  :  4  or 
1:3:6.  Such  proportions  mean  absolutely  nothing,  as  the 
proper  portions  of  materials  cannot  be  determined  until  the 
qualities  of  the  material  itself  are  known.  The  voids  vary  with 
all  the  material  all  over  the  United  States.  A  study  of  Bulletin 
No.  331*  on  the  subject  of  sand  will  show  that  there  is  a  wide 
range  of  variation,  first,  as  to  the  size  of  the  particles,  and  second, 
as  to  the  hardness  and  character  of  the  material  itself.  A  traprock 
with  a  high  compressive  strength  used  as  an  aggregate  in  a  certain 
proportion  will  give  a  concrete  of  much  higher  strength  than  an 
aggregate  of  very  soft  limestone.  If  a  contrac^tor  with  a  fixed 
proportion  cannot  obtain  2,000  lb.  or  with  any  variation  of  the 
proportions,  then  more  cement  must  be  used  or  another  aggregate 
obtained.  The  mere  fa(!t  that  his  material  in  standard  propor- 
tions will  not  give  2,000  lb.  in  my  mind  does  not  mean  that  he 

♦U.  S,  Geological  Survey. 


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Discussion  on  Aggregates.  499 

should  not  try  to  get  2,000  lb.  There  are  too  many  structures  Mr.  Humphrey, 
being  erected  in  this  country  assumed  to  have  a  strength  of  2,000 
lb.  and  upwards  where  as  a  matter  of  fact  the  strength  is  very 
materially  less.  The  sooner  more  attention  is  given  to  the  strength 
of  the  concrete  as  well  as  of  the  cement  and  the  steel,  the  better 
the  results  will  be. 

The  Joint  Committee  report  specifies  that  the  relation  of 
the  cement  to  the  aggregates  shall  be  1  to  6.  The  next  report 
will  contain  a  table  showing  the  strength  of  concrete  from  aggre- 
gates of  different  character  and  proportions,  so  that  for  any 
aggregate,  say  a  soft  limestone,  reference  to  the  table  will  show 
approximately  the  proportion  of  cement  and  aggregate  necessary 
to  obtain  a  2,000-lb.  concrete. 

Mr.  L.  R.  Ash. — In  connection  with  the  sand  and  grading  of  Mr.  Ash. 
aggregates  suggested  by  the  disintegrated  concrete  in  the  pier, 
the  water  put  into  a  mixture  sometimes  makes  considerable 
difference  and  also  the  depositing  of  concrete  in  or  through  water. 
I  want  to  call  attention  to  a  very  interesting  occurrence  here  in 
Kansas  City  a  couple  of  months  ago.  We  have  a  bridge  over 
the  Kaw  River  built  some  4  or  5  years  ago  and  lately  during  some 
very  intensely  cold  weather,  the  cylinder  pier  split  open  and  went 
down  so  badly  that  false  work  had  to  be  placed  to  hold  the  bridge 
up.  In  the  search  for  the  cause  the  first  suggestion  was  that  the 
contractor  had  not  put  in  any  cement  but  some  line  that  seemed 
to  be  accessible  in  the  neighborhood.  I  was  talking  to  the  fore- 
man of  the  job  and  he  told  me  the  circumstances,  which  it  seems 
to  me  would  explain  it  very  clearly.  The  concrete  was  deposited 
through  several  feet  of  water  with  the  result  that  there  were  layers, 
at  intervals,  of  material  more  like  laitance  than  anything  else, 
which  was  chalky  in  its  consistency  and  would  absorb  great  quan- 
tities of  water.  To  me  this  very  thoroughly  explained  the  break- 
ing down  of  the  concrete.  I  have  frequently  noticed  in  depositing 
concrete  that  small  pockets  or  irregularities  in  the  distribution 
of  the  water  would  crdate  conditions  that  would  show  up  badly, 
and  entirely  outside  of  any  irregularities  in  the  aggregate  at  all. 
Sometimes  I  think  that  is  a  matter  which  is  overlooked  in  the 
handling  of  concrete  and  depositing  of  the  same  in  the  forms. 

Mr.  Kinney. — I  would  like  to  ask  whether  anyone  has  noticed  Mr.  Kinney, 
in  the  fracture  of  gravel  concrete  that  the  pebbles  pull  out  rather 


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500  Discussion  on  Aggregates. 

Mr.  Kinney.  than  break?  This  was  particularly  noticeable  even  at  six  months 
in  these  building  code  tests  and  it  occurred  to  me  that  it 
might  be  a  characteristic  of  all  gravel  concrete  in  the  early  stages 
of  hardening. 

If  anyone  contemplates  the  making  of  test  cylinders  on  a 
job  or  in  the  laboratory,  I  might  add  that  we  have  found  a  very 
satisfactory  form  made  of  galvanized  iron.  This  form  consists  of 
a  flat  piece  of  galvanized  iron  16  in.  wide  and  long  enough  to  come 
together  and  be  soldered  to  form  an  8-in.  cylinder.  The  bottom 
is  circular  and  slightly  larger  in  diameter  than  8  in.  and  is  soldered 
to  the  cylinder.  With  the  use  of  a  sharp  instrument  these  soldered 
joints  can  be  readily  opened  and  the  forms  stripped.  Such  forms 
cost  22  cts.  apiece  and  they  are  worth  the  price. 

Mr.  Humphrey.  PRESIDENT  HUMPHREY. — Whether  or  uot  tcsts  of  Cylinders 

would  show  a  fracture  through  the  gravel  itself,  depends  largely 
on  the  age  and  the  proportions.  A  proportion  of  1  :  3  :  6  probably 
up  to  a  year  might  not  show  such  a  failure.  In  many  tests  made 
in  St.  Louis  the  gravel  did  fail,  especially  1:2:4  mixtures.  The 
fracture  was  right  through  the  particle,  even  the  hardest  particles. 
The  governing  factor  seems  to  be  the  manner  in  which  the  materials 
are  handled;  that  is,  the  character  of  the  concrete  and  its  age. 
A  well  made  gravel  concrete  of  1  :  2  : 4,  or  in  which  there  is  one 
part  of  cement  to  six  parts  of  gravel,  at  the  end  of  six  months 
should  certainly  show  a  fracture  through  the  gravel. 


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FIELD  INSPECTION  AND  TESTING  OF  CONCRETE. 
By  G.  H.  Bayles.* 

In  the  spring  of  1910  we  were  commissioned  to  design  and 
superintend  the  construction  of  a  warehouse  100  x  210  ft.,  4 
stories  high,  in  the  Borough  of  Brooklyn,  New  York,  for  the  New 
York  Dock  Company.  The  use  of  reinforced  concrete  was 
recommended  and  adopted,  but  from  experience  and  knowledge 
of  the  many  criticisms  of  this  material  and  the  considerable  num- 
ber of  failures  in  its  use,  it  was  decided  that  very  careful  inspec- 
tion should  be  maintauied.  Consequently  when  the  work  started 
in  the  latter  part  of  July  the  engineer  who  designed  the  building 
was  put  in  charge,  assisted  by  two  inspectors,  both  experts  in  the 
making  and  placing  of  reinforced  concrete.  The  engineer  assumed 
general  charge  of  the  work.  One  inspector  superintended  the 
proportioning  and  mixing  of  the  concrete  and  the  other  the 
placing  in  the  forms.  They  collaborated  in  the  inspection  of  con- 
structing and  wrecking  forms,  placing  reinforcement  and  testing 
materials. 

The  results  of  the  tests  on  the  above  work  were  on  the  whole 
so  satisfactory  and  the  information  obtained  was  deemed  of  such 
importance  that  they  were  continued  on  some  other  work  during 
the  summer  and  fall  of  1911.  This  latter  work  consisted  of  the 
reconstruction  of  a  block  of  six  warehouses.  The  whole  block  is 
210  X  374  ft.  in  plan  and  4  stories  high.  The  buildings  were  of 
the  old  type,  brick  walls  with  wood  interior.  All  the  wood  was 
removed  and  replaced  by  reinforced  concrete,  mak'mg  the  build- 
ing fireproof  throughout.  As  this  work  was  done  with  greater 
despatch  than  the  first  job  it  was  thought  best  to  have  more 
inspectors.  Consequently  a  chief  inspector  was  put  in  charge  of 
the  whole  work,  assisted  by  one  inspector  on  the  proportioning 
and  mixing,  one  on  the  placing  concrete  and  one  solely  for  making 
tests.  This  arrangement  worked  very  satisfactorily  and  allowed 
the  engineer  to  devote  more  of  his  time  to  other  work. 

There  seemed  to  be  no  recognized  system  of  testing  concrete 

*  AraiBtant  to  J.  W.  Galbreath.  ConBulting  Engineer,  New  York.  N.  Y. 

(501) 


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502     Bayles  on  Inspection  and  Testing  of  Concrete. 

or  concrete  materials  on  the  job,  so  a  series  of  tests  was  arranged 
to  meet  what  were  believed  to  be  the  necessary  requirements. 
These  tests  were  for  cement:  fineness,  constancy  of  volume,  time 
of  setting,  initial  and  final,  specific  gravity  and  crushing  strength 
of  1:  2  cement  mortar;  for  sand:  tests  for  loam,  fineness  and 
percentage  of  voids;  for  stone:  tests  for  percentage  of  voids; 
for  concrete:  tests  of  the  crushing  strength.  No  tests  of  the 
reinforcement  were  made  on  the  job. 

A  temporary  laboratory  was  built  near  the  work  and  the 
necessary  apparatus  installed.  This  laboratory  was  intended  to 
Ix*  such  as  could  be  built  on  any  job  and  no  arrangements  were 
made  for  heating  it  except  the  use  of  a  small  oil  stove  in  extreme 
weather.  It  was  12  x  8  ft.,  built  of  |-in.  sheeting  on  2  x  4  in. 
frame  ^vith  felt  roof;  one  door  front,  and  windows  one  side  and 
rear. 

cement  tests. 

At  first  6  samples  for  testing  were  taken  from  every  car  of 
cement,  but  later  this  number  was  reduced  to  3.  For  fineness 
the  usual  100-mesh  and  200-mesh  sieves  were  used.  The  inspector 
shook  the  sieves  in  his  hands  and  judged  by  the  eye  when  no 
appreciable  quantity  of  cement  was  going  through.  Scales 
graduated  to  milligrams  were  used  to  determine  the  proportions. 
A  nearby  tinsmith  made  the  boiler  and  wire  rack  for  the  con- 
stancy of  volume  tests  and  the  glass  plates  were  cut  on  the  job 
from  scrap  window  glass.  The  boiler  is  15  in.  high  and  8  in.  in 
diameter  with  a  lid,  and  the  rack  was  made  to  hold  12  pats  at  a 
time.  The  test  pats  were  boiled  for  5  hours  or  more.  The  Vicat 
needle  was  used  to  determine  the  time  of  setting.  The  variable 
temperature  made  the  remits  of  these  tests  vary  so  greatly  as  to 
be  of  little  value.  Le  Chatelier's  specific  gravity  apparatus  was 
used  with  gasoUne  for  determining  the  specific  gravity. 

The  test  for  crushing  strength,  not  being  in  such  general  use 
as  the  other  tests,  requires  more  detailed  description.  It  consisted 
in  testing  to  failure  4-in.  cubes  of  1 :  2  cement  and  sand  mortar. 
More  elaborate  apparatus  was  necessary  for  making  these  tests. 
For  this  purpose  were  required  gang  molds  for  the  cubes,  a  damp 
closet  large  enough  to  hold  4  gang  molds,  pans  of  water  in 
which  to  submerge  the  test  pieces,  and  a  compression  testing 


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machine.  The  gang  molds,  Fig.  1,  were  'made  of  1-in.  lumber 
held  together  by  iron  clamps.  The  measm-ements  were  not  exact, 
but  the  surface  areas  were  approximately  correct  within  the  limits 
of  accuracy  of  the  tests.  While  only  2  cubes  were  used  for  each 
test  the  gang  molds  were  made  for  4  cubes,  as  the  same  molds 
were  to  be  used  for  the  concrete  tests.  They  were  made  by  a 
carpenter  on  the  job  and  the  clamps  were  made  by  the  com- 
pany's blacksmith. 

The  damp  closet  was  built  into  the  comer  of  the  laboratory, 
the  sides  and  floor  of  the  laboratory  forming  two  sides  and  the 
bottom  of  the  closet;  the  other  sides  and  top  were  of  J-in. 
tongued  and  grooved  sheeting.     Two  shelves  were  put  in  the 


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FIG.    1. GANG   MOLD    FOR   4-IN.  CUBES. 

closet,  each  large  enough  to  hold  2  gang  molds,  and  space  was 
left  below  for  a  large  pan  of  water.  When  a  mold  with  test 
pieces  was  placed  in  the  closet  a  wet  coffee  sack  was  thrown 
over  it,  the  ends  of  the  sack  dipping  into  the  water  below.  A 
better  arrangement  would  be  to  have  the  closet  lined  with  felt, 
the  lower  edge  of  the  felt  dipping  into  the  water.  The  simpler 
method  was  used  as  being  one  easily  provided  on  any  job. 

The  pans  for  water  in  which  the  test  pieces  were  to  be 
submerged  were  made  28  x  28  in.  and  5  in.  deep,  large  enough  to 
hold  36  cubes  each.  The  same  size  pan  was  used  in  the  damp 
closet.  Five  pans  were  required  and  they  were  made  by  one  of 
the  company's  sheet  metal  workers. 


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504     Bayles  on  Inspection  and  Testing  of  Concrete. 

The  selection  of  a  compression  testing  machine  was  more 
difficult.  Most  machines  designed  to  do  this  kind  of  work  are  elab- 
orate and  expensive.  A  simple  and  comparatively  inexpensive 
machine  was  desired  and  after  careful  investigation  a  hydraulic 
machine  was  acquired,  consisting  essentially  of  two  horizontal 
plane  surfaces  between  which  the  test  pieces  are  crushed.  The 
top  surface  is  fixed,  being  held  rigidly  in  place  by  two  side  posts 
extending  upward  from  the  base.  The  lower  or  movable  surface 
is  fixed  rigidly  on  top  of  a  5-in.  cylindrical  ram  with  cup  leather 
packing  moving  in  a  copperlined  cylinder.  The  pressure  is 
applied  by  means  of  a  hand  pump  and  is  measured  on  a  gauge 
reading  total  tons  on  the  5-in.  ram.  The  gauge  is  graduated  from 
0  to  60  t.  and  while  the  rated  capacity  of  the  press  is  50  t., 
cubes  were  crushed  which  required  as  much  as  60  t.  pressure. 
As  many  of  the  newer  cubes  crushed  at  low  pressure  and  «xact 
readings  on  the  gauge  that  was  furnished  on  the  machine  were 
difficult,  a  second  gauge  was  attached  reading  up  to  10  t.  only. 
When  cubes  requiring  a  greater  pressure  were  being  tested  this 
second  gauge  was  shut  off  by  a  valve. 

On  account  of  the  high  values  which  were  obtained  at  the 
beginning  of  the  work  suspicion  was  directed  towards  the  accuracy 
of  the  machine,  but  comparisons  of  the  cubes  by  testing  on  an 
accurately  gauged  machine  at  the  testing  laboratory  of  Columbia 
University  showed  that  the  small  press  used  on  the  work  was 
correct  within  reasonable  limits*  (see  Table  IV). 

For  each  test  2  cubes  of  1 :  2  cement  and  sand  mortar  were 
made.  The  sand  used  was  taken  from  that  used  on  the  work 
and  was  washed  clean.  To  insure  uniformity  a  sufficient  quan- 
tity for  all  the  tests  was  taken  at  one  time  and  stored  in  a  bin 
until  required.  For  each  test  a  little  in  excess  of  128  cu.  in.  of 
sand  and  half  as  much  by  volume  of  cement  were  used.  The 
sand  and  cement  were  mixed  dry,  then  sufficient  water  added  to 
make  a  fairly  wet  mixture,  that  is,  one  that  was  readily  puddled 
but  would  not  pour.  The  whole  was  then  well  mixed  and  placed 
in  the  molds  and  puddled  ^vith  a  small  trowel.  All  the  operations 
were  done  by  hand.  As  soon  as  the  mortar  was  sufficiently  set 
to  hold  the  markings  the  date  and  hour  were  marked  on  both 

*  A  dcBcriptiou  of  a  test  of  a  similar  machine  is  given  in  Engineering  Neva,  February  11, 
1909,  p.  167. 


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Bayles  on  Inspection  and  Testing  op  Concrete.     505 

cubes  and  the  mold  placed  in  the  damp  closet.  At  the  end  of 
24  hours  the  mold  was  taken  from  the  damp  closet,  the  forms 
removed  and  one  cube  crushed.  The  other  cube  was  submerged 
in  a  pan  of  water  where  it  remained  for  6  days  and  was  then 
crushed.     All  were  tested  to  failure. 

To  prevent  little  inequalities  of  the  surfaces  of  the  cubes 
from  seriously  affecting  the  results  three  thicknesses  of  blotting 
paper  were  used  top  and  bottom  of  each  cube  in  the  press.  After 
some  time  it  was  discovered  that  the  long  sides  of  the  gang  molds 
were  more  nearly  parallel  than  the  others  and  thereafter  care  was 
taken  to  use  the  sides  of  the  cubes  formed  by  them  as  the  crush- 
ing faces.  By  this  means  better  and  more  nearly  uniform  results 
were  obtained. 

SAND  tests. 

Every  scow  load  of  sand  was  tested  for  percentage  of  loam. 
If  the  sand  in  different  parts  of  the  scow  appeared  to  be  of  dif- 
ferent quality  more  than  one  test  was  made.  This  test  consisted 
in  taking  a  quantity  of  sand  and  drying  it  thoroughly  on  a  stove. 
A  thousand  grams  of  it  was  then  taken  in  a  12-quart  pail  and 
washed  by  turning  on  a  hose,  giving  the  water  as  it  flowed  from 
the  hose  just  sufficient  velocity  to  keep  the  mass  stirred  up  and 
moving,  the  loam  being  carried  off  in  the  overflow.  When  the 
water  ran  clear  the  sand  was  again  dried  and  weighed,  the  dif- 
ference in  weight  giving  the  percentage  of  loam.  Sand  contain- 
ing more  than  2  per  cent  was  rejected. 

Tests  were  also  made  to  determine  the  comparative  fineness 
of  the  sand.  These  were  only  made  when  there  appeared  to  the 
eye  to  be  a  difference  in  the  grade.  The  test  consisted  in  taking 
a  measured  quantity  of  sand  (by  weight)'  and  screening  it  by 
hand  through  20-mesh  and  30-mesh  sieves.  These  tests  showed 
on  an  average  about  21  per  cent  retained  on  the  20-mesh  sieve, 
27  per  cent  on  the  30-mesh  sieve  and  the  remainder  passing 
through  the  30. 

Occasional  tests  for  percentage  of  voids  in  the  sand  were 
made  as  follows:  A  comparatively  large  amount  of  sand  was 
measured  and  weighed  to  show  the  average  weight  per  cu.  cm. 
Then  a  quantity  by  weight  corresponding  to  50  cu.  cm.  was  put 
into  a  glass  graduate  and  the  volume  of  water  displaced  meas- 


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506    Batles  on  Inspection  and  Testing  of  Concrete. 

ured.     The  average  volume  of  voids  was  thus  found  to  be  about 
40  per  cent. 

stone  tests. 

As  the  grade  of  the  crushed  stone  varied  but  slightly  only 
occasional  tests  were  made  to  determine  the  percentage  of  voids 
in  the  stone.  To  do  this  a  quantity  of  stone  was  submerged  in 
water  for  2  hours  to  permit  it  to  become  thoroughly  saturated. 
The  water  was  then  poured  off  and  the  stone  exposed  to  the  air 
half  an  hour  to  permit  the  surface  moisture  to  evaporate.  A 
vessel  of  known  capacity  (nearly  10,000  cu.  cm.)  was  then  filled 
with  the  stone  and  weighed.  Sufficient  water  was  added  to  fill  all 
the  voids  and  the  weight  taken  again.  The  difference  in  weight 
showed  the  percentage  of  voids.  As  there  was  excess  of  voids 
around  the  sides  of  the  vessel  this  test  is  only  comparative  and  is 
not  considered  particularly  important  as  the  inspector  can  best 
judge  by  the  appearance  of  the  batch  when  the  voids  are  prop- 
erly filled.  For  the  stone  used  on  this  work  the  voids  measured 
by  the  above  method  averaged  nearly  50  per  cent.  Measure- 
ments of  concrete  in  place  and  stone  on  the  scows  indicated  that 
the  volume  of  stone  used  was  about  97.5  per  cent  that  of  the  con- 
crete produced. 

concrete  tests. 

What  seemed  to  be  the  most  important  test  and  the  test 
of  most  practical  value  was  that  of  the  crushing  strength  of  the 
concrete  itself  as  it  was  placed  in  the  forms  for  the  building. 
For  these  tests  the  same  apparatus  was  used  as  for  the  mortar 
tests.  The  preparation  of  the  test  pieces  was  simpler.  The 
gang  mold  for  four  4-in.  cubes  was  taken  onto  the  work  where 
concrete  was  being  poured.  The  concrete  was  taken  from  the 
buggies  as  it  was  being  poured  into  the  forms  and  was  imme- 
diately placed  in  the  cube  mold  and  puddled  with  a  small  trowel. 
There  was  no  excessive  puddling  as  it  was  intended  to  approx- 
imate working  conditions  as  nearly  as  practicable.  One  and 
sometimes  two  tests  were  made  every  day  concrete  was  poured. 
From  this  time  on  the  operation  was  similar  to  that  for  testing 
mortar.  After  24  hours  in  the  damp  closet  the  forms  were 
removed,  1  cube  crushed  and  the  3  others  submerged  in  a  pan  of 


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water.  Of  these  3  one  was  crushed  at  the  end  of  7  days,  1  day 
in  the  damp  closet  and  6  in  water,  one  at  the  end  of  28  days  and 
the  other  was  removed  from  the  water  at  the  end  of  28  days  and 
laid  aside  to  be  tested  later. 

As  has  already  been  said,  no  attempt  was  made  to  preserve 
an  even  temperature  in  the  laboratory,  the  object  being  to  main- 
tain as  nearly  as  practicable  the  condition  of  the  concrete  in  the 
work,  so  that  it  sometimes  happened  during  the  winter  that  ice 
formed  on  the  water  in  the  pans  where  the  test  cubes  were  sub- 
merged. The  effect  of  this  is  clearly  shown  in  the  results  of  the 
tests.  A  practical  use  of  the  tests  of  concrete  was  to  indicate  to 
the  inspector  as  well  as  the  contractor  the  safe  time  for  wrecking 
forms.  This  time  was  fixed  at  first  at  7  days,  but  was  afterwards 
shortened  to  4  days  during  the  summer  and  well  into  the  fall, 
when  the  decreasing  strength  of  the  cubes  tested  caused  the  time 
to  be  again  extended  to  7  days. 

results  of  tests. 

There  is  nothing  notable  in  the  results  of  the  tests  for  fine- 
ness, constancy  of  volume  and  specific  gravity,  except  that  they 
show  what  may  be  expected  from  the  ordinary  insi>ector  who  is 
not  specially  trained  in  making  such  tests  and  where  the  tests 
are  made  under  the  conditions  prevailing  on  the  ordinary  job. 
The  results  of  the  tests  for  initial  and  final  set  were  so  varied, 
due,  no  doubt,  to  the  changing  temperature,  that  they  lack 
value  as  determining  the  quality  of  the  cement. 

Tests  of  the  cubes  of  1:  2  cement  and  sand  mortar  were 
intended  to  show  a  definite  relation  of  strength  of  the  cement 
being  tested  to  what  could  be  expected  from  the  concrete  made 
from  the  cement.  Comparisons  of  the  results  of  these  tests  with 
the  results  of  the  tests  of  concrete  were  so  simple  and  proved  so 
satisfactory  that  it  is  believed  they  show  with  sufficient  accuracy 
the  practical  rate  of  setting  of  the  cement  and  that  the  tests  for 
initial  and  final  set  could  be  discontinued  for  field  laboratories. 

Strength  of  Mortar. — The  173  tests  of  1 :  2  cement  and  sand 
mortar  on  the  first  job  showed  an  average  compressive  strength 
of  448  lb.  per  sq.  in.  in  24  hours  and  2110  lb.  per  sq.  in.  in  7  days. 
On  the  second  job,  where  a  different  brand  of  cement  was  used, 
198  tests  were  made  and  the  average  compressive  strength  was 


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508     Bayles  on  Inspection  and  Testing  of  Concrete. 

585  lb.  per  sq.  in.  in  24  hours  and  2100  lb.  per  sq.  in.  in  7  days. 
Table  I*  shows  in  detail  the  results  of  the  tests  on  the  former  and 
Table  II  those  on  the  latter  job.  The  results  are  recorded  as 
found  with  the  inspector's  notes,  the  dates  alone  being  omitted 
for  lack  of  space.  In  Table  I  the  first  50  tests  were  made 
between  August  17  and  October  3,  1910,  the  next  50  between 
October  3  and  November  21,  1910,  the  next  50  between  Novem- 
ber 21,  1910,  and  January  25,  1911.  The  remaining  23  were 
made  between  January  25  and  March  16,  1911.  In  Table  II 
the  first  50  tests  were  made  between  July  11  and  August  24, 
the  next  49  between  August  24  and  September  22,  the  next  50 
between  September  22  and  October  21  and  the  remaining  49 
between  October  21  and  November  25,  all  in  1911. 

Strength  of  Concrete, — The  235  tests  on  concrete  cubes  on 
the  first  job  showed  an  average  compressive  strength  at  28  days 
of  3450  lb.  per  sq.  in.  and  on  the  second  job,  96  tests,  2321  lb. 
per  sq.  in.  at  28  days.  The  tests  on  concrete  cubes  were  carried 
on  from  August,  1910,  to  December,  1911,  tests  being  made  nearly 
every  day  except  during  the  month  of  February,  1911,  when  no 
work  was  done  on  account  of  inclement  weather,  and  from  the 
completion  of  the  first  job  in  May,  1911,  until  the  beginning  of 
the  second  job  in  July  following.  During  the  latter  part  of 
December,  1910,  and  throughout  January,  1911,  the  sand  and 
water  used  in  making  the  concrete  were  heated  so  that  the  batch 
had  a  temperature  of  60  to  65  deg.  when  placed  in  the  forms. 
Table  III  shows  the  complete  record  of  the  tests  on  concrete 
cubes  on  the  first  job,  and  Table  IV  those  on  the  second  job, 
both  giving  the  inspector's  notes  of  variations  from  the  rule. 
While  there  are  considerable  variations  of  strength  from  the 
maximum  to  the  minimum  most  of  the  cubes  crushed  near  the 
average  and  reference  to  the  final  results  indicates  that  the  varia- 
tions were  due  more  to  the  method  of  testing  than  to  the  quality 
of  the  concrete,  for  while  a  cube  crushed  after  24  hours  may  have 
been  below  the  average,  the  cube  of  the  same  set  crushed  after 
28  days  was  about  as  often  above  the  average  as  below  it  and  vice 
versa.     It  seems  evident  that  the  actual  strength  of  the  concrete 


*  The  insiK'ctor's  notes  give  all  the  strength  testa  in  tons  per  4-in.  cube,  but  (or  convenience 
of  compaiison  with  other  testa  the  results  have  been  converted  into  lb.  per  sq.  in.  in  printing 
the  tables. — Ed. 


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Table  I. — ^Tests  of  Cement  and  1  :  2  Mortar. 


Car 

Number. 


1 
2 
3 

4 
5 

f  1 
2 
3 
4 
6 
6 

f  1 
2 
3 
4 

,  5 

1 
2 
3 
4 
6 
6 

1 
2 
3 
4 
5 
6 

1 
2 
3 

4 
5 


1 
2 
3 
4 
5 
6 

1 
2 
3 

f  1 
2 
3 
4 
5 
6 

1 
2 
3 

4 
5 
6 


Percentage  of  Cement. 


Retained  on  Sieve. 


100  Mesh.  200  Mesh 


11.250      23.800 


7.150 
5.870 
7.210 


7.050 

8.260 
8.300 
7.455 
7.400 
7.080 
8.020 

6.980 
6.130 
6.300 
6.070 
7.170 

6.830 
7.050 
6.790 
5.700 
5.450 
6.960 

5.950 
6.600 
6.270 
7.110 
6.500 
7.000 

8.370 
8.300 
8.100 
5.720 
7.200 
6.450 

8.400 
7.450 
8.100 
7.900 


20.075 
25.010 
21.050 


Through 
200Meflh. 


64.860 


72.100 
68.430 
71.160 


20.300   71.850 


20.630 
21.400 
18.560 
23.310 
21.490 
22.520 

22.140 
20.700 
21.520 
23.140 
19.000 

20.100 
25.020 
22.940 
22.750 
21.800 
22.850 

20.720 
21.120 
21.270 
24.250 
22.400 
17.020 

20.120 
19.600 
19.550 
17.750 
19.030 
18.620 

19.750 
19.800 
19.870 
20.880 


70.620 
69.750 
73.730 
71.250 
70.000 
68.770 

70.490 
72.850 
72.000 
70.300 
73.100 

73.050 
67.830 
69.050 
71.330 
72.490 
70.110 

i  73.250 
'  72.050 

72.250 
'  68.550 

71.100 
I  75.700 

t  71.470 
71.800 
72.000 
76.380 
73.600 
74.800 

71.600 
72.650 
72.000 
71.000 


6.950 
6.490 


18.900 
18.300 


73.900 
74.700 


Setting. 


Initial. 
Hre. 


m 


2H 

1'^ 


4 
4 

4H 
4 

3H 

3>5 

4 

2H 

3*4 

4H 
4>^ 


3H 


4 
3 

2H 


4 


2H 
'3'" 


6.500 
6.420 
5.900 
6.070 
5.550 
5.320 

4.650 


20.330 
18.850 
17.500 
18.050 
17.700 
17.170 


72.970  ' 

74.700  I 

76.500 

75.800 

76.650 

77.460 


3 


Final. 
Hrs. 


16.550   78.720 


6.490 
"5  .'850 


19.050   74.490  | 
18.520  '75.430 


2% 
3     ■ 


2H 


314 


4^ 

4 

5H 


7 

6^ 

6 

5H 
5 

7 
7 
3M 

5 

6>i 

6% 


6^ 


7 


Crushing 
Strength 
Specific  I  of  4-in.  cubes. 
Gravity   in  lb.  persq.  in. 


3.1 


3.15 
3.13 
3.11 
3.11 
3.15 

3.07 
3.12 
3.12 
3.13 
3.10 
3.12 

3.15 
3.14 
3.12 
3.12 
3.11 

3.15 
3.15 
3.16 
3.17 
3.13 
3.12 

3.12 
3.13 
3.12 
3.14 
3.12 
3.13 

3.12 


6H    3.09 
'3.10' 


5>i 
■5"* 


5'i 


5 


0>4 


3.14 
3.13 
3.14 
3.12 
3.13 
3.13 

3.09 
3.13 
3.14 

3.09 
3.11 
3.12 
3.12 
3.06 


Boiling 
5  hours. 


24  hrs.  7  days. 


3.09 
3.12 


3.10 
3.11 
3.11 


500 
563 
500 

1053 
1250 
1000 
1188 
1125 

750 
1250 
657 
500 
500 
845 

875 
813 
813 
375 
500 

750 
750 
750 
1025 
600 
813 

500 
475 
625 
500 
500 
525 

750 
875 
875 
875 
813 
875 

688 
750 
625 
688 
750 
625 

625 
875 
625 

375 
438 
438 
438 
563 
313 

1125 
1250 
938 
438 
375 
438 


2125 
2315 

2583 
3190 
2350 
3190 
3220 

1870 
2500 
2290 
2150 
2350 
2230 

2780 
2370 
2275 
1940 
2750 

2650 
2400 
1975 
3350 
2230 
2750 

2625 
2625 
2775 
2500 
2310 
2190 

2125 
2500 
2500 
2500 
2500 
2625 

2.500 
2750 
2625 
2250 
2250 
2370 

3000 
3500 
2625 

2065 
2813 
2875 
2250 
3130 
1880 

2870 
2440 
2500 
2630 
2500 
3190 


O.K. 


O.K. 
O.  K. 
O.  K. 
O.  K. 
O.K. 

O.K. 
O.  K. 
O.K. 
O.  K. 
O.  K. 
O.K. 

O.K. 
O.K. 
O.  K. 
O.K. 
O.K. 

O.  K. 
O.  K. 
O.  K. 
O.K. 
O.  K. 
O.K. 

O.K. 
O.  K. 
O.  K. 
O.  K. 
O.  K. 
O.  K. 

O.K. 
O.  K. 
O.  K. 
O.  K. 
O.K. 
O.K. 

O.K. 
O.  K. 
O.  K. 
O.  K. 
O.  K. 
O.K. 

O.K. 
O.  K. 
O.  K. 


0. 

K. 

0. 

K. 

0. 

K. 

0. 

K. 

O.  K. 

O.K. 
I  O.  K. 
i  O.  K. 


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510     Bayles  on  Inspection  and  Testing  of  Concrete. 


Table  I. — Tests  of  Cement  and  1  :  2  Mortar.  (Continued  ) 


Car 

Number. 

Setting. 

Initial.     Final. 
Hr».    1    Hrs. 

Specific 
Gravity 

Retained 
lOOMesh. 

on  Sieve. 
200Me8h. 

Through 
200Me«h. 

f  1 
2 
3 
4 
6 

.6 

[  1 
2 
3 

4 
6 

ie 

f  1 

2 
3 

4 
6 
6 

1 
2 
3 
4 
6 
A 

8.270 

29.520 

72.120 

2H 

* 

3.14 

L 

8.200 

19.220 

72.200 

2H 

4K 

3.12 

7.960 

18.710 

'73.300 

2H 

4H 

3.12 

M 

8.110 
8.000 

19.040 
18.660 

72.760 
73.180 

3 

5 

5 

3.12 
3.12 

7.000 

19.620 

73.260        Z}i 

6 

7.600 

19.010 

73.260 

4H 

6^ 

3.08 

n 

7.680 

18.620 

73.670 

4>i 

6 

3.13 

7.499 

18.400 

73.880   ;     4H 

3.12 

7.090 

18.960 

73.900        ZH 

55i 

3.13 

o 

7.200 

19.570 

73.160   i     4 

h^i 

3.12 

7.330 

20.300 

72.190 

3 

4H 

3.13 

f  1 

P        2 

7.610 
7.730 
7.860 

6.400 
7.000 
7.720 

7.600 
7.100 
7.260 

6.060 
4.770 
3.860 

4.480 
6.910 
6.710 

6.940 
7.070 
7.320 

7.300 
7.610 
7.560 

6.200 
6.350 
6.530 

6.490 
6.440 
7.030 

6.330 
6.430 
6.920 

20.620 
16.370 
20.410 

20.900 
21.210 
18.050 

20.680 
16.760 
20.760 

20.300 
20.400 
14.060 

17.360 
18.780 
23.730 

20.030 
19.300 
19.500 

17.700 
18.860 
21.650 

18  500 
18.000 
20.940 

19.040 
19.530 
18.910 

18.660 
18.780 
18.790 

71.560 
76.700 

2H    ' 

3.14 
3.11 
3.13 

3.13 
3.12 
3.09 

3.08 
3.07 
3.09 

3.15 
3.12 
3.12 

3.12 
3.12 
3.12 

3.11 
3.11 
3.13 

3.12 
3.13 
3.13 

3.11 
3.13 
3.14 

3.12 
3.13 
3.14 

3.14 
3.12 
3.13 

3 

71.690 

f  1 

«  ll 

1 

R        2 

3 

f  1 

8         2 

,3 

f  1 
T        2 

72.620 
71.780 
73.650 

71.620 
76.030 
71.860 

73.440 
74.700 
82.030 

78.160 
76.260 

4H 
6 

6H 

I'A 

6 
6 

6 
6 
6K 

6« 

13 

r  1 

U        2 
3 

f  1 

V  2 
3 

f  1 

W        2 

3 

f  1 

X        2 

3 

f  1 

Y  2 
3 

69.600 

72.560 
73.400 
73.170 

75.000 
73.500 
70.550 

75 . 150 
75.470 
72.510 

74.320 
74.020 
73.850 

74.970 
74.740 
74.200 

7K 

hV^ 
6K 
5H 

5Ji 

6^4 

84 

XA 

.•■>}4 

6 

8 
8 

IS 

7 
7 
9 

8 
8 

Crushing 

Strength 

of  4-in.  cubes, 

inlb.  persq.  in. 


24  hrs.  I  7  days. 


1188 
1188 
1125 
400 
438 
476 

876 
1126 
1125 
1125 
1250 

938 

538 
563 
563 
563 
626 
438 

375 
500 
438 
438 
438 
600 

438 
438 
438 

600 
513 
676 

625 
638 
600 

188 
188 
250 

250 
188 
188 

250 
250 
250 

188 
188 
188 

313 
313 
250 

313 
250 

288 

275 
275 
313 


2260 
2500 
2630 
2000 
2500 
2625 

2625 
2376 
2376 
2625 
3250 
2500 

2250 
2375 
2600 
2875 
2500 
3125 

2437 
2750 
2500 
2500 
2875 
2626 

2000 
1876 
2065 

2376 
2250 
2275 

2500 
2625 
2188 

2260 
2250 
2260 

2688 
2250 
2313 

2188 
2260 
2250 

1875 
1750 
1875 

2000 
1937 
1750 

1937 
1750 
2375 

2125 
2312 
2500 


Boiling 
5  hours. 


O.K. 
O.K. 
O.K. 
O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 
O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 
O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 
O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 

O.K. 
O.  K. 
O.K. 

O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 

O.K. 
O.  K. 
O.  K. 

O.  K. 
O.  K. 
O.  K. 

O.  K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 


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Bayles  on  Inspection  and  Testing  of  Concrete.      511 


Table  I.- 

—Tests  of  Cement  and  1 

:  2  Mortar. 

{Continued  ) 

Car 
Number. 

Perce 
Retained 
lOOMeahy 

Qtage  of  Cement 

Sett 

Initial. 
Hrs. 

ing. 

Final. 
Hrs. 

Specific 
Gravity 

Crushing 

Strength 

of  4-in.  ctibea, 

inlb.  pcrsq.in. 

Bofling 
5  hours. 

on  Sieve. 
200Mesh. 

18.450 
19.000 
19.280 

Through 
200Meah. 

74.900 
73.960 
73.330 

24  hrs. 

313 

438 
250 

7  days. 

f  1 

Z         2 

3 

6.630 
7.030 
7.240 

5>i 

8H 
6>i 

3.13 

2375 
2063 
2125 

O.K. 
O.K. 
O.K. 

f  1 

AA       2 

3 

7.100 
6.980 
7.350 

21.280 
23.500 
19.430 

71.470 
69.100 
73.140 

6 

6 

3.12 
3.11 
3.12 

138 
200 
200 

1250 
1625 
1688 

O.K. 
O.K. 
O.K. 

1 
BB       2 

l3 

6.160 
7.000 
6.440 

18.110 
19.730 
19.270 

74.670 
73.250 
74.230 

8 
8 

8H 
9ki 

3.14 
3.13 
3.13 

125 
188 
200 

1250 
1500 
1025 

O.K. 
O.K. 
0.  K 

1 

CC       2 

3 

6.600 
6.350 
6.380 

21.330 
18.650 
22.140 

71.980 
74.800 
71.450 

9 

10 

3.09 
3.12 
3.12 

125 
125 
125 

1437 
1250 
875 

O.K. 
O.K. 
O.K. 

DD    1  2 

l3 

4.950 
5.110 
5.000 

17.360 
18.550 
16.960 

77.650 
76.220 
77.960 

6 
6 
7^ 

7 
7 

3.11 
3.14 
3.11 

125 
160 
126 

1813 
1188 
1000 

O.K. 
O.K. 
0.  K 

1 

EE       2 

3 

5.050 
4.460 
4.660 

18.150 
17.670 
20.350 

76.700 
77.810 
74.980 

3.12 
3.12 
3.07 

126 
126 
138 

1937 
1250 
1400 

O.K. 
O.K. 
O.K. 

FFJI 

4.440 
4.730 
6.000 

17.450 
19.480 
19.050 

78.070 
75.770 
75.920 

h 

3.11 
3.09 
3.11 

150 
138 
138 

1400 
1437 
1313 

O.K. 
O.  K. 
O.K. 

f     1 

GG       2 
3 

5.000 
5.250 
5.430 

19.500 
20.650 
22.260 

74.860 
73.700 
72.050 

3M 
3K 

3.11 
3.09 
3.12 

150 
150 
163 

1437 
1625 
1563 

O.K. 
O.K. 
O.  K. 

1 

HH       2 

3 

4.960 
4.850 
4.950 

21.750 
19.050 
19.020 

73.030 
76.000 
75.900 

2K 
35i 

3K 
3K 
4>i 

3.14 
3.07 
3.12 

150 
150 
138 

1437 
1500 
1126 

O.K. 
O.K. 
O.K. 

'  1 

•II        2 

^  3 

5.140 
6.010 
5.800 

19.080 
20.520 
21.310 

75.650 
74.380 
72.830 

¥ 

2H 

3.12 
3.11 
3.14 

125 
88 
126 

1188 
1063 
1375 

O.K. 
O.K. 
O.K. 

f  1 
JJ       2 

7.420 

21.920 

70.420 

5k 

5H 

3.12 

125 
150 
160 

1437 
1538 
1563 

O.K. 
O  K 

13 

7.640 

23.660 

68.650 

3.08 

O.K. 

f  1 

KK   \  2 

3 

10.230 
10.290 
9.500 

23.930 
23.500 
24.800 

65.600 
66.000 
65.500 

6 

6H 

3.12 
3.16 
3.16 

188 
160 
138 

1376 
1313 
1275 

O.K. 
O.K. 
O.K. 

f  1 

LL       2 

3 

7.030 
8.200 
6.300 

22.260 
23.900 
20.370 

70.600 
67.900 
73.230 

6 
6 
6 

8 
8 
7H 

3.12 
3.12 
3.11 

188 
150 
138 

1663 
1500 
1625 

O.K. 
O.K. 
O.K. 

MM  1  2 

9.350 
10.320 
10.520 

6.850 
6.850 
7.120 

22.500 
23.930 
23.610 

27.170 
25.900 
23.230 

68.000 
65.580 
65.700 

65.740 
67.000 
69.480 

6 
6 

7H 

3.15 

126 
138 
188 

188 
163 
150 

1313 
1313 
1376 

1126 
1437 
1376 

O.K. 
O.  K. 

u 

3.14 

3.062 
3.107 
3.137 

O  K 

1 

NN   ■   2 
3 

7 
7 
7 

f  1 

OO       2 

3 

6.750 
7.660 
6.980 

23.450 
24.260 
22.930 

69.050 
67.800 
70.000 

7 

8K> 

;;;;;;; 

3.137 
3.122 
3.137 

126 
100 
126 

1250 
1313 
1250 

f  1 

7.370 
7.020 
7.050 

22.830 
21.450 
21.800 

69.600   { 
71.300    ! 
71.040 

9 
9 
7 



75 
38 
38 

1125 
1260 
1376 

PP       2 

3 

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512     Bayles  on  Inspection  and  Testing  of  Concrete. 


Table  I. — Tests  of  Cement  and  1  :  2  Mortar.     (Continued.) 


Car 

Number. 


QQ 


RR 


8S 


li 


Percentage  of  Cement 


Retained., on  Sieve. 


Setting. 


Through    initial 

100 Mesh.  200 Mesh.  200 Mesh.,    Hra. 


6.700 
6.670 
6.860 

6.000 
7.100 
4.840 


Final. 
Hrs. 


Specific 
Gravity 


22.570  70.450 

21.180  I    72.960 

21.900  I    70.900 

17.750  76.800 

24.100  68.680 

18.760  76.280 


7.800  23.320 
7.660  22.460 
7.300   '    22.160 


68.630  8 
69.730  9 
70.440   '     9 


Crushing 

Strength 

of  4-in.  cubes, 

inlb.  persq.in. 


24  hrs.    7  days. 


125 
125 
150 

150 
113 


1626 
1688 
1626 

1750 
1876 


125  I  1876 


3  122 
3.107 


163 
163 
150 
150 


1375 
1375 
2000 
1875 


Boiling 
5  hours. 


and  the  strength  which  can  be  safely  counted  on  in  construction 
is  rather  above  than  below  the  average  of  the  tests  made. 

requirements  for  materials  and  concrete. 

The  values  given  in  Tables  III  and  IV  are  not  necessarily 
true  of  all  concrete,  and  perhaps  it  would  not  be  amiss  to  describe 
in  some  detail  how  this  concrete  was  made. 

In  order  that  good  concrete  may  be  produced  the  first 
requirement  is  that  the  specifications  be  correct,  full,  exact  and 
clear.  This  enables  the  inspector  to  do  his  work  on  a  definite 
plan  without  the  annoyance  of  possible  objections  or  interference 
by  the  contractor's  superintendent,  who  is  sometimes  more 
interested  in  the  quantity  than  the  quality  of  the  product.  With 
this  object  in  view  the  specifications  were  made  for  this  work. 
Following  are  the  items  appl>'ing  to  the  materials  and  manufac- 
ture of  concrete: 

Concrete  will  be  composed  of  one  (1)  part  cement,  two  (2)  part^  sand  and 
four  (4)  parts  stone,  with  sufficient  water  to  make  a  wet  mixture.  The 
cement,  sand  and  stone  will  be  introduced  into  a  batch  mixer  of  approved 
design  and  the  mixer  given  3  turns  before  the  water  is  added.  After  the  wat^r 
is  added  the  mixer  will  be  revolved  at  least  12  times  and  to  the  satisfaction 
of  the  engineer  before  the  batch  is  dumped.  Concrete  must  be  placed  immedi- 
ately after  mixing  and  well  spaded  to  insure  a  dense  concrete. 

Cement,  where  used  in  these  specifications,  will  mean  Portland  cement 
of  such  quality  as  to  meet  the  standard  specifications  of  the  American  Society 
for  Testing  Materials,  and  stand  the  tests  pre^scribed  in  the  rules  and  regula- 
tions of  the  Bureau  of  Buildings,  Borough  of  Brooklyn,  City  of  New  York. 


Digitized  by 


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Bayles  on  Inspection  and  Testing  of  Concrete.     513 


Table  II. — ^Tests  of  Cement  and  1  :  2  Mortar. 


Q 

ar 
nber. 

Percentage  of  C 

ement 

Through 
200  Mesh. 

Setting. 

Initial.  1  Final. 
Hrs.     1     Hrs. 

Specific 
Gravity 

Crushing 

Strength 

of  4-in.  cubes, 

in  lb.  per  sq.  in. 

Boiling 
5  hours 

Nut 

Retained 
100  Mesh. 

on  Sieve. 
200Meah. 

24  hrs. 

7  days. 

A 

H 

5.93 

6. 

6.28 

18.97 
19.15 
20.20 

74.90 
74.70 
73.50 

ig 

2M 

3 
3 
2»i 

3.152 
3.122 
3.137 

450 
563 
469 

1938 
2375 
2125 

O.K. 
O.K. 
0.  K. 

B 

f  1 
2 
3 

6.36 
5.75 
6. 

19.26 
18.41 
18.71 

74.26 
75.75 
75.22 

v 

lu 

3 

2}4 

2H 

3.152 
3.152 
3.137 

750 
844 
875 

2313 
2188 
2563 

0.  K. 
O.K. 
O.K. 

C 

f  1 
2 
3 

6.7 

7.26 

6.75 

19.85 
19.90 
19.90 

73.25 
72.70 
73.22 

2H 

1».4 

2 

2»yi 

2H 

2»4 

3.122 
3.137 
3.137 

688 
513 
594 

2125 
1750 
1813 

O.K. 
0.  K. 
O.K. 

D 

f  1 
2 
3 

6.14 
5.04 
6.09 

20.21 
19.82 
15.65 

73.43 
74.01 
77.94 

2 
2 

2 

2?4 

3 

3>i 

3.137 
3.16S 
3.152 

406 
406 
406 

2000 
1938 
2063 

O.K. 
O.K. 
O.K. 

E 

1^ 

3 

6.32 

6.5 

6.17 

20  02 
18.20 
19.21 

73.51 
75.21 
74.48 

2 
2 
2 

2H 

3.152 
3.122 
3.122 

313 
469 
388 

1875 
19.38 
2000 

O.K. 
O.K. 
O.K. 

F 

ll 
13 

5.38 
6.67 
6.41 

20.02 
16.98 
19.36 

74.39 
76.09 
74.06 

3K 

4 

3.152 
3.152 
3.168 

475 

388 
438 

1875 
1688 
1938 

O.K. 
O.K. 
O.K. 

G 

f  1 
2 
3 

5.07 
6.32 
6.39 

19.83 
20.13 
20.38 

74.86 
73.38 
73.08 

3 

4 

3»4 

4 

3.152 
3.152 
3.137 

375 
525 
531 

2125 
2813 
1813 

O.K. 
O.K. 
O.K. 

H 

f  1 
2 
3 

6.61 
6.13 
5.92 

18.84 
19.06 
19.41 

74.29 
75.58 
74.43 

2'<i 
2^ 

S14 

3?4' 

3'^i 

3.137 
3.152 
3.152 

.531 
563 
531 

2188 
2188 
2000 

O.K. 
O.K. 
0.  K 

I 

f  1 
2 
3 

6.17 
5.06 
6.18 

18.92 

19.09. 

19.32 

74.68 
75.53 
74.29 

3 

3«4 

^1 

3.168 
3.152 
3.168 

531 
525 
513 

2125 
2125 

2188 

O.K. 
O.K. 
0.  K. 

J 

f  1 
2 
3 

6.13 
7.73 
7.20 

18.84 
18.96 
17.64 

74.81 
73.08 
74.93 

2H 

4'2 

4 

3.137 
3.16K 
3.137 

500 
625 
563 

2125 
2250 
2250 

O.K. 
O.K. 
O.K. 

K 

f  1 

{  2 

3 

6.17 
5.81 
6.13 

17.86 
19.07 
19.20 

75.61 
74.89 
74.38 

3 
2^ 

2H 

4>i 

4 

4 

3.152 
3.152 
3.168 

438 
388 
538 

2125 
2188 
2000 

O.K. 
O.K. 
O.K. 

L 

f  1 
2 
3 

5.86 
5.12 
6.09 

18.42 
18.63 
19.13 

75.41 
75.93 
74.59 

2H 

4 

4^ 

4M 

3.137 
3.168 
3.168 

450 
531 
325 

2125 
2063 
2000 

O.K. 
O.K. 
O.K. 

M 

(  1 

2 

,  3 

5.16 
6.03 
5.82 

19.13 
18.79 
19.03 

75.38 
74.92 
74.97 

4 

4 
4M 

3.168 
3.152 
3.152 

613 

688 
5.'>0 

2313 
2375 
2063 

O.K. 
O.K. 
O.K. 

N 

f  1 
2 
3 

5.20 
5.43 
6.12 

19.41 
19.21 
19.02 

75.13 
75.19 
74.70 

3^ 
3H 

3M 

4j.i 

3.152 
3.137 
3.152 

525 
600 
538 

2125 
2438 
2188 

O.K. 
O.K. 
O.K. 

0 

f  1 
2 
3 

6.12 
5.87 
6.02 

18.80 
19.21 

18.84 

74.91 
74.79 
75.01 

35i 

AH 

434 

4^4 

3.168 
3.168 
3.152 

563 
550 
775 

2125 
1875 
2313 

O.K. 
O.K. 
O.K. 

P 

f  1 
2 
3 

5.82 
6.45 
8.24 

19.63 
19.47 
17.14 

74.38 
73.43 
74.14 

4 

5 
5 
6 

3.168 
3.168 
3.137 

594 
525 
525 

2250 
1938 
1938 

O.K. 
O.K. 
O.K. 

Q 

f  1 

2 

.3 

7.42 
9.76 
7.40 

17.39 
19.31 
18.39 

75.02 
70.80 
74.03 

3H 

4 

3>i 

3.152 
3.152 
3.137 

313 
250 
450 

2125 
1875 
2250 

O.K. 
O.K. 
O.K. 

Digitized  by 


Google 


514    Bayles  on  Inspection  and  Testing  of  Concrete. 


1 

rABLE  11 

Percei 
Retained 
100  Mesh. 

6.47 
9.50 
8.96 

.— Tests 

of  Cemc 

sment 

Through 
200Me8h. 

nt  and 

Sett 

Initial. 
Hrs. 

4 
3^ 

4H 

1  :2\ 

ing. 

Final. 
Hrs. 

lortar. 

Specific 
Gravity 

3.137 
3.168 
3.152 

{Conlinued) 

Crushing 
Strength 

of  4-in.  cubes. 

in  lb.  per  sq.  in. 

Car 

Number. 

atage  of  d 
on  Sieve. 
200  Mesh. 

Boiling 
5  hours. 

24  hrs. 

300 
300 
219 

7  days. 

1 

R        2 

3 

18.33 
16.24 
16.88 

75.02 
74.08 
74.05 

F 

2250 
1938 
1875 

O.K. 
O.K. 
0.  K. 

[  1 

S         2 

,  3 

8.66 
9.34 
8.12 

17.20 
16.70 
16.91 

74.02 
73.81 
74.83 

3' '2 

4'a 

4H 

4*4 

5' 2 

3.168 
3.168 
3.152 

300 
225 
219 

1625 
1750 
2000 

O.K. 
0.  K. 
O.K. 

1 

T        2 

3 

6.79 
7.04 

8.48 

18.62 
17.47 
16.60 

74.41 
75.30 
74.81 

5'4 

6>i 
5H 

6»4 

6'i 
6>i 

3.137 
3.122 
3.168 

125 
100 
113 

1875 
1625 
1875 

O.K. 
O.K. 
O.K. 

1 

U     {  2 

3 

8.43 
5.87 
7.70 

17.05 
18.92 
17.84 

74.37 
74.97 
74.29 

6 

5»4 

5^4 

7*4 

8 

74 

3.152 
3.152 
3.168 

113 
106 
88 

1938 
2188 
1688 

O.K. 
0.  K. 
O.K. 

V     1  2 

l3 

6.88 
7.13 
6.84 

17.92 
18.22 
18.39 

74.94 
74.47 
74.51 

4j; 

3*4 

6 
5 
5 

3.122 
3.152 
3.152 

475 
438 
438 

1963 
1875 
2000 

O.K. 
O.K. 
O.K. 

W     1  2 
13 

7.31 

8.48 
8.82 

18.06 
14.70 
16.93 

74.48 
76.59 
74.97 

3M 

3 

3 

5 

4H 
4h 

3.122 
3.162 
3.152 

419 
425 
288 

2125 
2313 
2063 

O.K. 
0.  K. 
O.K. 

Mi 

9.03 

7.14 
8.23 

16.17 
17.09 
16.18 

74.62 
75.49 
75.44 

4  4 

4H 
4H 

6 

3.137 
3.168 
3.168 

213 
181 
150 

1938 
1875 
1688 

O.K. 
O.K. 
O.K. 

Y     11 

13 

7.13 
8.08 
8.32 

17.95 
16.69 
18.17 

74.79 
75.06 
73.29 

4% 
4h 
4H 

6 

3.152 
3.137 
3.122 

169    1    1750 
325    1    2188 
294        2000 

O.K. 
O.K. 
O.K. 

f  1 

Z         2 

3 

7.93 
8.12 
6.92 

18.31 
18.22 
18.05 

73.49 
73.43 

74.88 

4H 
4».i 
4,4 

61 2 

3.137 
3.152 
3.137 

263 
250 
288 

1625 
1437 
1563 

O.K. 
0.  K. 
O.K. 

f  1 

AA       2 

3 

8.72 
7.88 
9.47 

18.39 
18.27 
17.62 

72.74 
73.60 
72.79 

4H 

6K 
64 
6»i 

3.122 
3.122 
3.152 

288 
350 
350 

1563 
1688 
1437 

O.K. 
O.K. 
O.K. 

f  1 

BB       2 

3 

11.40 
9.13 
8.72 

18.70 
18.99 
18.04 

69.78 
71.64 
73.07 

k 

64 

3.152 
3.137 
3.137 

363 
344 
213 

1437 
1500 
1437 

O.K. 
O.K. 
O.K. 

1 

CC       2 

3 

6.93 
8.31 
8.43 

19.09 
19.01 
18.77 

73.84 
72.43 
72.63 

4H 
4'i 
434 

3.137 
3.107 
3.122 

219        1813« 
238    I    2«>3« 
282    1    1875> 

O.K. 
O.K. 
O.K. 

r  1 

DD       2 
3 

8.70 
7.93 
8.41 

17.34 
18.04 
18.57 

73.84 
73.71 
72.83 

4l'l 
4H 
4H 

5H 
54 

3.137 
3.137 
3.122 

338    '    2063« 
344        20002 
350    1    2375» 

O.K. 
O.K. 
O.K. 

EE    I2 
l3 

12.24 
9.17 
8.41 

16.84 
17.32 
18.69 

70.79 
73.24 
72.74 

4H 

4U 
6U' 

6 

3.152 
3.152 
3.137 

275        2063 
344    1    2188 
313        2250 

O.K. 
O.K. 
O.K. 

1 

FF       2 

3 

9.96 
9.22 
8.43 

17.58 
17.93 
18.34 

72.29 
72.61 
73.02 

6 
64 

7M 

3.122 
3.137 
3.137 

319        2000 
244        1875 
250    ,   ^000 

O.K. 
O.K. 
O.K. 

f  1 

GG       2 

3 

10.92 
13.30 
11.76 

18.63 
18.95 
18.72 

70.12 
67.50 
69.06 

6 

5>4 

5h 

7H 

3.184 
3.122 
3.122 

175    1    1563 
275        1375 
100    1    1563 

O.K. 
O.K. 
O.K. 

HH  J2 
3 

4.75 
5.28 
5.15 

19.31 
24.87 
21.62 

75.9 

69.72 

73.12 

2 
214 

2U 

3)i 

3.12 

3.2 

3.152 

938 
1063 
1063 

2500 
2000 
3063 

O.K. 
O.K. 
O.K. 

>  Eight  days 

. 

Digitized  by 


Google 


Batles  on  Inspection  and  Testing  of  Concrete.    515 


Car 

II 

f  1 
2 
3 

JJ 

li 

KK 

f  1 
2 
3 

LL 

f  1 

2 

,3 

MM 

f  1 
2 
3 

NN 

f  1 
2 
3 

GO 

f  1 
2 
3 

PP 

f  1 
2 
3 

QQ 

f  1 

2 

.3 

RR 

f  1 
2 
3 

SS 

f  1 
2 
3 

TT 

f  1 
2 
3 

UU 

1 
2 
3 

VV 

f  1 
2 
3 

Table  II, — ^Tests  of  Cement  and  1  :  2  Mortar.     {Continued) 

Setting. 


Percentage  of  Cement 


Retained  on  Sieve. 
100 Mesh.  200 Mesh. 


WW 


XX 


YY 


(1 
II 


5.36 
7.82 
6.47 

4.75 
5.46 
5.83 

5.00 
5.13 
5.09 

6.64 
6.23 
6.06 

5.18 
6.05 
6.13 

5.97 
6.13 
5.99 

7.10 
5.94 
6.12 

5.68 
6.32 
6.29 

6.13 
6.07 
5.84 

7.02 
6.87 
6.92 

4.53 
4.60 

4.87 

7.03 
6.61 
6.72 

5.87 
5.69 
6.12 

6.35 
5.86 
5.92 

5.88 
7.44 
6.78 

5.97 
6.31 
6.41 

6.74 
6.37 
7.01 


22.28 
26.06 
24.63 

25.93 
26.97 
24.66 

22.72 
21.87 
22.36 

23.01 
23.18 
21.61 

23.64 
24.16 
24.42 

23.19 
22.94 
21.82 

21.78 
22.31 
22.14 

25.04 
22.76 
24.07 

22.77 
22.69 
21.57 

23.62 
20.93 
22.17 

22.05 
20.66 
21.33 

23.65 

23.115 

22.95 

22.06 
23.12 
22.36 

24.13 
23.70 
23.15 

19.26 
23.01 
23.55 

23.82 
23.77 
21.95 

20.65 
22.06 
20.85 


Through 
200Me8h. 


72.19 
65.96 
68.79 

69.16 
67.44 
69.39 

72.16 
72.89 
72.47 

70.24 
70.47 
72.20 

71.06 
69.63 
69.30 

70.71 
70.85 
72.11 

71.01 
71.61 
71.60 

69.15 
70.79 
69.51 

71.01 
71.20 
72.28 

69.20 
72.08 
70.80 

73.05 
74.45 
73.61 

69.20 
69.80 
70.13 

71.91 
71.03 
71.40 

68.70 
70.21 
70.49 

74.45 
69.53 
69.41 

70.03 
69.61 
71.39 

72.40 
71.29 
71.98 


2 


2 
2 

2 

2 

2 
2 

IH 
IH 

2V^ 
2>i 

2 

2M 

IH 

1 

IM 

2H 

2?4 
2H 

2H 

2>4 

3 

2H 

2% 

2H 
2H 
2H 


Initial.!  Final 
Hrs.    I    Hrs. 


2M 
2H 
2 

24 

2H 

2H 

v^ 

2H. 

2 
2 
2 

2 

IH 


Crushing 
Strength        | 
Specific   of  4-in.  cubes,     Boiling 
Gravity!  in  lb.  per  sq.  in.  5  hours. 


O.  K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 

O.K. 
O.K. 
O.K. 


Pigitized  by 


Google 


516    Bayles  on  Inspection  and  Testing  of  Concrete. 

Tablk  II. — Tests  of  Cement  anil  1  :  2  Mortar.     (CorUinued) 


Car 

Number. 

PercentaRp  of  Comont 
Retained  on  Sieve.   ^^^^^^^ 
lOOMeah.  2(M)MeHh.  2(K)Me.sh. 

5.91          18.22         75.05 
6.(19          15.42     ;     77.75 
6.21          15.31         78.14 

Sett 
Initial. 

h™. 

IH 

Final. 
HrH. 

3 
3 

2»4 

1  Speeific 
Gravity 

3.168 
3.  IS.? 
3.122 

Crushing 

Strength 

of  4-in.  eubes. 

in  lb.  persq.  in. 

Boiling 
5  hours. 

24  hrs. 

938 

688 
625 

7  day  b. 

r  1 

ZZ        2 
.3 

2438 
2250 
2375 

O.K. 

.  O.  K. 

O.K. 

f  1 
AB    <  2 

is 

8.06 
5  52 
7.02 

17  93 
17  83 
20.05 

73.60 
75.33 
72.70 

2 

3 
2V 

2U 

3.152 
3.152 
3.152 

1 

563 
375 
375 

1088 
2000 
1750 

O.K. 
O.  K. 
O.K. 

f  1 

AC    \  2 

I  3 

9.20 
7.21 
0.92 

20 

19.03 

17.95 

70.66 
73.67 
75 

2 
2 
2 

F 

1  3.162 
'   3.152 
,  3.137 

1250 
1000 
1250 

2375 
2250 
2875 

O.K. 
O.K. 
O.K. 

f  1 

AD       2 

>  3 

8.35 

7 

7.47 

19.35 
19.80 
21.02 

72.12 
73.21 
71.51 

3  4 
33  a 

4 

!  3.137 
3.137 
3.137 

1125 
1188 
1063 

2125 
2063 
2438 

O.K. 
O.K. 
O.  K. 

f  1 
AE       2 

13 

6.84 

7 

6.30 

19.35 

20 

19.27 

73.60 
72.89 
74.35 

3 

VA 

3.137 

3.137 

1  3.137 

813^ 
938 
938 

2375' 
2125 
2250 

O.K. 
O.K. 
O.K. 

AF    1  2 

13 

6.44 
6.55 
6.9 

18.45 
18.5<i 
18.8 

75 

74.83 

74.07 

2h 

3 
3 

3.152 
3.152 
3.137 

813 
600 
438 

1750 
2188 
2313 

O.K. 
O.K. 
O.K. 

f  1 

AG       2 

3 

6.7 

6.12 

7.13 

18.71 
19.00 
19.28 

74.55 
74.61 
73.40 

3'4 

3 
3 

4 
4 
4 

3.137 

3.137 

j   3.152 

688 
625 
781 

1750 
1688 
1750 

O.K. 
O.  K. 
O.K. 

f  1 

AH       2 

3 

6.23 
5.47 
7.11 

19.66 
19.80 
18.80 

74.05 
74.58 
73.87 

2»4 
2«4 

3 

4M 
4 

4M 

3.152 

1  3.137 

3.137 

656 
875 

781 

2250 
2250 
2438 

O.K. 
O.K. 
O.K. 

AI     1  2 
3 

7.92 
8.46 
8.17 

20.08 
21.19 
20. .58 

71.80 

70 

70.71 

3 

2H 

3'.. 

4li 

1'^ 

3.137 
3.137 
3.137 

656 
719 
663 

2125 
2063 
2250 

O.K. 
O.K. 
O.K. 

AJ    1  2 

13 

7 

6.77 

5.76 

20.47 
21.21 
19.58 

72.32 
71.80 
74.53 

3 

2h 

1« 

3.137 
3.137 
3.137 

531 
503 
594 

2000 
2063 
2188 

O.K. 
O.K. 
O.K. 

1 

AK       2 

3 

6.09 
6.16 
6.04 

19.66 
19.98 
19.82 

74 

73.74 

74.09 

2H 
2H 

2H 

3 
3 
3 

3.152 

.  3.137 

3.152 

500 
375 
594 

1938 
1625 
2250 

O.K. 
O.K. 
O.K. 

f  1 
AL    {  2 

5 
5 
5.25 

19.45 
20.21 
20.19 

75.35 
74.70 
74.24 

2 

3 
3j.i 

:  3.168 

3.137 

,  3.152 

531 
600 
406 

2188 
2313 
168S 

O.K. 
O.  K. 
O.K. 

f  1 

AM   <  2 

l3 

6 

0.82 

7.37 

19.97 
18.20 
18.42 

73.63 

72 

74.03 

2 

2\i 
2'.i 
2U 

3.122 
3.137 
3.137 

638 
663 
513 

2188 
2188 
1813 

O.K. 
O.K. 
O.K. 

f  1 

AN       2 

3 

6.82 
6.53 
6  41 

20 

19.75 

19.90 

72.80 
73.45 
73.45 

f' 

2'i 

2'2 

3M 

3.152 

3.152 

1  3.137 

388 
531 
375 

1750 
2000 
1813 

O.K. 
O.K. 
O.K. 

f  I 

AG       2 

,  3 

5.95 
6.25 
6.42 

19.40 
19.05 
20.11 

74.50 
74.60 
73.35 

1?4 

3 
3 

2?4 

3.122 

3.137 

1  3.137 

475 

469 
481 

2750 
2250 
1813 

O.K. 
O.K. 
O.K. 

»  Sand  contained  58  per  cent  loam. 


Digitized  by 


Google 


Bayles  on  Inspection  and  Testing  op  Concrete.     517 


Table  III. — Crushing  Strength  of  4-in.  Concrete  Cubes. 


Strength  in 

Str'gth 

Arc 

in 

days. 

336 

1 

Strength  in 

Str'gth 

Age 

in 

days. 

Date  made. 

lb. 
24  hr. 

375 

per  sq.  in. 
7dy.  ,28dy. 

1250'  2425 

in 
lb.  per 
sq.  in. 

3688 

Date  made. 
_ 
11-17-10 

lb. 
24  hr. 

250 

per  sq.  m. 

7  dy.  !28dy. 

■  — 1 

2125*  35006 

in 
lb.  per 
sq.  in. 

8-18-10 

4688 

240 

8-18-10 

375   ....  2475 

3566 

336 

11-18-10 

188 

1750  2750^ 

5000 

241 

8-19-10 

500  1375  2500 

4088 

335 

11-19-10 

313 

1250  4250 

6260 

252 

8-19-10 

375 

19001  2188 

3750 

335 

11-21-10 

250 

1500  3375 

4375 

238 

8-20-10 

500 

1125  2875 

4250 

334 

11-29-10 

275 

1875  1  3500 

4750 

230 

8-22-10 

500 

1250  2225 

4500 

331 

1  11-30-10 

188 

1250  3726 

4875 

226 

8-25-10 

625 

2000  ,  2875 

4375 

329 

12-  1-10 

200 

1875  '  3125 

4375 

224 

8-25-10 

500 

2000  ,  3938 

5626 

328 

!  12-  1-10 

200 

1875  4938 

6750 

239 

8-26^10 

375 

1350  '  2875 

4375 

327 

12-  2-10 

200 

1875  :  3188 

4625 

223 

8-26-10 

375 

1750  1  2875 

4250 

322 

12-  5-10 

263 

1250  ;  2750 

4875 

225 

8-30-10 

375 

875  3000 

4376 

323 

12-  8-10 

188   1500  1  3188 

5000 

221 

8-31-10 

750  '  2275  i  3500 

4625 

321 

12-15-10 

200  1  2250  3438 

4750 

214 

9-  6-10 

875  ,  1975 

3500 

5000 

316 

12-19-10 

200  1  2375*'  4438 

&-  7-10 

438 

1688 

2500 

3875 

316 

12-20-10 

350  ;  1900  2938 

4125 

izi  2  ■ 

9-  8-10 

563 

1500 

3125 

4375 

313 

12-27-10 

250   1625  3250 

4875 

205 

9-13-10 

563  1375  3125 

4813 

308 

12-28-10 

313  2375  402.'^« 

6125 

203 

9-14-10 

500  1875  3375 

4626 

307 

12-28-10 

2.W 

1875  1  418^" 

4688 

201 

9-14-10 

438   1625  3250 

5063 

307 

12-29-10 

438 

3026  !  5563 

6125 

200 

9-15-10 

750 

1875  4375 

6250 

307 

1  12-30-10 

275 

2750  5500 

5500 

200 

9-15-10 

625 

2625  3813 

4813 

306 

1  1-  9-n 

188 

1600  3063 

4625 

189 

9-16-10 

563 

2250  3750 

5563 

306 

1-11-11 

150  1  1400  ,  2938 

3125 

190 

9-16-10 

600  2188  3750 

5000 

305 

1   1-12-11 

400  3150  1  4000 

7500 

197 

9-17-10 

375   1500  3125 

5250 

304 

1   1-12-11 

250 

1688  3750 

5000 

197 

9-19-10 

500   1938  2500 

5250 

303 

;   1-14-11 

250 

1625  1  3250 

4875 

195 

9-20-10 

688  ,  2250  3500 

4500 

302 

1-19-11 

225 

1438  3125 

4875 

190 

9-20-10 

813  2250  3938 

4500 

301 

1-19-11 

313 

1688  3125 

4500 

190 

9-21-10 

725  1875  3500 

4938 

300 

1   1-21-11 

150 

1313  2625 

3625 

188 

9-21-10 

563 

2125  !  37  .fin 

4760 

301 

1-23-1 1 

125 

1250  2025 

9-22-10 

563 

2500 

3600 

5875 

294 

:   1-23-11 

150 

1313  i  2500 

4250 

im ' 

9-22-10 

500 

1875 

2938 

4375 

299 

1-24-11 

338 

1625  2625 

3750 

185 

9-23-10 

750 

2250 

2688 

5376 

298 

1-26-11 

262 

1250  2375 

4125 

168 

9-23-10 

438 
500 

2000 
2250 

3125 
3125 

1-26-11 
1  3-  8-11 

438» 
188 

1250  2250 
1625  j  3250 

3500 
4750 

183 

9-24-10 

'  4688  ' 

299 

124 

9-26-10 

1000 

1750 

2500 

4688 

297 

!  3-  8-11 

200 

1750  1  287.-) 

4376 

124 

9-27-10 

600  1875 

3500 

4188 

294 

3-  9-11 

175 

1938  2875 

9-27-10 

875  1875 

3125 

4626 

296 

3-  9-11 

225 

1975  ,  3938 

■  '4875  ■ 

124 

9-28-10 

563 

1575 

2750 

3750 

294 

3-10-11 

188  ■  1876 

3750 

5813 

132 

9-29-10 

500 

2063 

3000 

4260 

292 

3-10-11 

263  2375 

5625 

5625 

121 

9-30-10 

563 

1875 

2875 

4125 

293 

1  3-11-11 

250 

2500 

5000 

7188 

123 

10-  3-10 

2.'>0 

1250 

2000 

3125 

288 

1   3-13-11 

313 

2188 

4813 

65(K) 

121 

10-  4-10 

500 

2125 

3125 

4938 

289 

3-14-11 

2.50  2750 

4625 

6750 

128 

lO-U-lO 

500 

2000 

2750 

3500 

279 

3-14-11 

188  2125,4188 

6250 

118 

10-13-10 

375 

1875 

2813 

4313 

277 

3-18-11 

188 

2250  5500 

6125 

116 

10-14-10 

500 

1750 

2750 

4250 

276 

!  3  20-11 

350 

2500  !  4750 

7125 

114 

10-15-10 

375 

1875 

2250 

3563 

273 

1   3-20-11 

288  2500  4375 

5625 

114 

10-17-10 

500  2250 

2938 

4813 

274 

3-21-11 

375  3(X)0  i  4750 

6625 

113 

10-19-10 

500 

1250  2000 

4375 

268 

3-21-11 

275  2500  5000 

6875 

112 

10-19-10 

688 

1875  2750 

4750 

269 

3-23-11 

313  2375  1  5000 

5750 

110 

10-25-10 

313 

1250  !  2250 

3625 

261 

3-30-11 

250 

2.500  1  4625 

6750 

103 

10-25-10 

313 

1375  ;  2260 

3126 

262 

3-31-11 

150 

2000  1  4875 

6260 

101 

10-26-10 

375 

2063  2688 

4625 

266 

4-  1-11 

313 

2563  5250 

7600 

102 

10-28-10 

350 

1688  2938 

4876 

264 

4-  3-11 

250 

2500  .  4625 

6126 

100 

1O-31-10 

250 

1563  2000 

4375 

256 

4-  3-11 

250 

2625  5000 

5125 

100 

10-31-10 

263 

1250  2750 

4750 

256 

4-  5-11 

250 

2125  4625 

6000 

98 

10-31-10 

313 
313 

2125 
1750 

3125 
2750 

4-  6-11 
4-13-11 

375 
375 

2.563 
3125 

4500 
4625 

5125 
6625 

96 

11-  1-10 

4938 

i260 

89 

11-  2-10 

500 

1250 

2875 

6875 

251 

4-13-11 

438 

3125 

4750 

6126 

88 

11-  2-10 

725 

2125 

2875 

4003 

2.58 

4-14  11 

375 

2750  4625 

5625 

89 

11-  7-10 

350 

2438 

4600 

6500 

250 

4-14-11 

43810 

3375-^  5625 

4750 

89 

11-  7-10 

313  2250  4125 

6063 

255 

4-15-11 

563" 

2250  3500 

4375 

34 

11-  9-10 

313  2250  3125 

5500 

246 

4-18-11 

375 

1625  3600 

4625 

85 

11-10-10 

350 

1625  3125 

4750 

247 

4-22-11 

260 

1625  1  3375 

4063 

79 

11-10-10 

375 

1500 

3000 

6000 

246 

4-25-11 

375 

1875  3750 

4750 

78 

11-11-10 

250 

2000 

3125 

4125 

245 

4-27-11 

438 

2375  '  4375 

6125 

76 

11-11-10 

188 

2000 

3125 

5125 

2.>0 

4-28-11 

750  2500  5000 

6875 

74 

11-12-10 

250 

2125 

27505 

5875 

248 

5  8-11 

500  2250  4125 

5000 

64 

11-14-10 

188 

1375 

2375 

4250 

243 

5-12-11 

626   1875  4375 

5000 

60 

11-15-10 

225 

1750 

3813 

5875 

246 

5-18-11 

625  2250  4.375 

5375 

54 

11-16-10 

188 

1250 

2500 

4188 

241 

5-20-11 

875  1750  3625 

4063 

52 

11-16-10 

313 

2125* 

3125 

1 

: 

1  14  days 

<12 

days. 

» 27  daj 

^8.               W 

21  hours 

»  30  hour 

B,          •8  c 

lays. 

•29  da] 

fS,                                    » 

53  hours 

>  30  days 

•70 

days 

»  43  hoi 

ITS. 

r~>^ 

' 

Dig 

tized  by 

Gc 

518    Baylbs  on  Inspection  and  Testing  of  Concrete. 


Table  IV. — Crushing  Strength  of  4-in.  Concrete  Cubes. 


Date  made. 


7-15-11 
7-17-11 
7-lS-n 
7-18  11 
7-19-U 
7-24-H 
7-25~n 
7-25-11 
7-afl-ll 
7-2fl-ll 
7-31-n 
8-  J-H 
ft-  J-il 
8-  2-11 
8-  2-il 
S-  3-11 

8-  3-n 

8-  4-11 

8-  4-11 
8^-  8-11 

8-  li-ll 
S'l&-]1 
8-11-11 
S-ll-ll 
8-H-ll 
SI- II  11 
8-lt>-ll 
8-18-11 
8-25-11 
8-28-11 
8-28-11 

9-  1-11 
9-  1-11 
9-  2-11 
9-  5-11 
9-  7-11 
9-  8-11 
9-12-11 
9-13-11 
9-14-11 
9-16-11 
9-18-11 
9-18-11 
9-19-11 
9-20-11 
9-20-1 1 
9  21-11 
9-22-11 


IK  p{!r  b(}k  In, 
!J4hr   7dy.  l2Rdy 


lOOOJi; 
50;t 
08^ 

75LJ 

esH 
7at3 

5m 
m:i 

^35   I 
62A  I 

essM 

BOtI 
625 

as8 

525 

sea 
Si:i 
5fla 

635 

m>» 
56:* 
fi2V 

4;^9  I 

563   ! 

563 

625 

563 

563 

375 
1250* 

625 

500 

375 

563 

375 

500 

9387 

325 

450 

487 

413 

438 

438 
1500» 


1500  |2lS8 
1750  1^875 


1750  3I8S 

1500  2rm 

I37f»  2375 

11125  2S75 

1375'*  2813 

ViJii  ims 

rim  '2ms 

12505  2im 
15(XI^  22r»o 
i:j7/i  '.utm^ 
m:i   2i:iji 

125C]  2750 
llStH  if500 
150tl    287,'i 

Umii    2125 

iOf>:i  iihH 
H7:j    ntiK 

li;S5*  2260 
1188  2.563 
1313  2313 
1125  2188 
1000  ,1813 
1375  '3188 
1250  2(525 
1188  2813 
1250  12500 
1125  ,2625 
875  2063 
1063  1 2688 
1063« '2563 
1063  J2438 
1375  2563 
1000  12250 
1188  2250 
1188  2375 
1250*  1938 
1500»  2250 
15(K)  2563 
1688  12875 


in  I  Age 
lb.  per  ,  ,»° 
aq.  in.  I  days. 


I  i 

I  116»  I 

I  177  I 

,  115»  I 

!  176 

I  109»  I 

'  170  I 

I  170 

1  107» 

I  169  I 
102>,, 


Date  made. 


Strength  in 
lb.  per  aq.  in 


,24  hr.  7  dy.  '28dy.|  aq.  in. 


3625 
3950 
4875 
4519 
5000 
4031 
5063 
4000 
4313 
4688 
4269 


I  2938 

3813 

1  3875 

4069 

4519 

5125 

4169 

I  4288 

I  5625 

,  3625 

3637 

!  3875 

3719 

I  .3875 

I  3438 

,  4063 

I  3788 

3750 

3138 

4813 

I  4.375 

3938 

4625 

I  3688 

3875 

5000 

4125 

4375 

4.500 

39,38 

I  3813 

I  42.')0 

34.38 

4063 

4250 

4875 


38  1 
1001 
100» 

991 

99» 
*98» 
<98«  I 

94» 
155 
154 

91» 
1.53 

881  I 
1.50 

861  I 
146 

771 

1.36 

136 

1.32 

132 

131 

128 

126 

125 

121 

120 

119 

117 

115  I 

115 

114  i 

113 

113 

112 

111 


^  Broken  at  Columbia  University. 

*  6  days,  7  hours. 

*  5  day^,  2  hours. 

*  Contained  6  per  cent  loam,  extra  10  per 
oent  cement  used. 

*  5  days. 

*  3  days. 

'  53  hours. 


9-25-11 
9-25-11 
9-27-11 
9-28-11 
9-28-11 
10-  2-11 
10-  2-11 
lO-  3-11 
10-  3-11 
10-  5-11 

10-  6-11 
10-10-11 
10-10-11 
10-12-11 
10-12-11 
10-16-11 
10-17-11 
10-17-11 
10-19-11 
10-20-11 
10-23-11 
10-24-11 
10-25-11 
10-26-11 
10-30-11 
10-31-11 

11-  1-11 
11-  2-11 
11-  2-11 
11-  3-11 
11-  4-11 

11-  6-11 
11-11-11 
11-1.3-11 
11-13-11 
11-14-11 
11-14-11 
11-17-11 
11-20  11 
11-20-11 
11-21  11 
11-22-11 
11-24-11 
11-28-11 
11  2t)-ll 
11-29-11 

12-  1-11 
12-  1-11 


719 

6.50 

688 

388 

344 

263 

294 

469 

438 

419 

4.38 

438 

388 
i  375 
I  375 

406 

375 

450 

325 

294  I 

300 

.344 

263  1 

263 

263 

300  . 

238  I 

113"> 

lOO" 
I   ..", 

250" 

400»i 
I  450"; 
I  94  ' 

169 

2.50  1 

275  I 

125 

225  I 

194  • 

331 

100 

175 

200 
•'188>a 
"156"! 
,  219 

156 


2250 
2313 
24.38 
2000 
2188 
2313 


I 


1375 
1313 
1625* 
1000 
875 
9.38 
875  ;2063 
1188  2563 
1125« 12063 
1000  2250 
1063  |2813 
1063  2188« 
1188«;18757| 
1063  I2OOO 
875  11938  I 
1000  2063  I 
969  12313 
1.500«  ,2438 
788  '2125 
825  11875 
788  I2I88  ' 
919  2063  I 
800»  11813  ' 
675  17,50  I 
888  12875  | 


969  12563 
600t  1 2125 
469  12063  I 
400  i2188  I 
6.56»|l625  1 
600  12438  , 
781  ;i625  I 
663  I2OOO 
4,38  11625 
588  19.38  I 


713 

788 
875> 
800 
888 
1125 


1625 

19.38 

1813  I 

1625 

1813 

2000 


I 


813  '2000 
7.50  13063 
1000  1938 
688  ,1688 
875u!l813 
719  11,563 
869  ,1813 


4500 
4000 
4625 
3625 
3625 
3813 
3625 
4375 
3688 
3625 
4250 
4250 
3563 
3688 
3875 
4125 
4313 
4188 
4063 
3375 
3438 
3875 
3688 
3375 
5125 
5063 
3625 
3875 
3875 
3625 
3438 
3438 
2875 
3250 
3000 
3000 
3250 
3125 
2813 
3125 
3125 
.3000 
4438 
3063 
2500 
2188 
2625 
3250 


Age 

in 
dasrs. 


108 
108 
106 
105 
105 
101 
101 
100 
100 
98 
97 
93 
93 
91 
91 
87 


84 
83 
80 
79 
78 
77 
73 
72 
71 
70 
70 
69 
68 
66 
61 
59 
59 
58 
58 
55 
52 
52 
51 
50 
48 
44 
43 
43 
41 
41 


•6  days. 

•29  days. 
"  Cube  not  set. 

11  Cube  broke  when  removed  from  forms. 
"  48  hours. 
"  9  days. 
»« 4  days. 
»  7  days. 


Digitized  by 


Google 


Bayles  on  Inspection  and  TESTnjra  op  Concrete.     519 

All  sand  must  be  washed,  clean,  sharp,  silicious  and  free  from  injm'ious 
matter. 

Ail  stone  shall  be  clean  crushed  trap  rock,  free  from  dust  and  to  contain 
no  particle  that  will  not  pass  through  a  f-in.  ring. 

There  was  little  diflSculty  in  getting  satisfactory  materials. 
Standard  brands  of  Portland  cement  were  used.  The  sand  was 
what  is  known  in  New  York  as  "Cow  Bay,"  and  was  satisfactory 
with  a  few  exceptions  when,  for  some  reason,  it  was  impossible  to 
get  washed  sand  from  the  usual  source  and  other  sands  were  tried 
temporarily  to  take  its  place  in  order  not  to  delay  the  work. 
Some  of  this  sand  was  satisfactory,  some  was  condemned  out- 
right and  one  scow  load  was  accepted  on  condition  that  lO  per 
cent  additional  cement  be  used, — a  doubtful  expedient.  The  stone 
was  a  Hudson  Palisades  trap,  commercial  J-in.  size  and  proved 
generally  acceptable. 

operation  of  plant. 

The  mixer,  a  batch  mixer,  was  set  in  a  pit  so  that  the  top  of 
the  receiving  hopper  was  a  little  above  the  floor  of  the  wharf. 
The  sand  and  stone  were  measured  approximately  in  wheel- 
barrows or  buggies  and  the  cement  by  the  bag,  reckoning  a  bag  of 
cement  at  0.95  cu.  ft.  The  aggregates  were  all  put  in